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Many foreign students choose to do part-time work to help pay their tuition or living expenses. Today, eight out of ten foreign students are engaged in some type of part-time work in Japan (Source: JASSO survey 2009). However, under the status of residence of "exchange student," which is given to foreign students, they are originally allowed to reside in Japan for the purpose of studying at school, and it is not permitted for foreign students to work for a paid job. Therefore, if anyone resides in Japan with the status of "exchange student" and still wishes to take a paid part-time job, he/she is required to obtain an official permission called shikakugai katsudo kyoka (Permit to Engage in Activity other than that Permitted by the Status of Residence Previously Granted) from the nearest regional immigration bureau. In such a case, the students must observe the condition that such paid work will not interfere with their schoolwork, which is their original purpose of residence in the country. As an exemption, no such permission is required since July 2010 for activities as educational/research assistants who are paid and work based on a contract with a university or a technical college to which an applying student belongs. (Note: For technical college students, only those who are in the 4th and 5th grade or in advanced courses are eligible for this exemption)
 
Obtaining a permit to work from the immigration bureau
For foreign students who wish to work part-time, the first thing to do is to apply for and obtain a shikakugai katsudo kyoka (Permit to Engage in Activity other than that Permitted by the Status of Residence Previously Granted) at the nearest regional immigration bureau.
To apply, applicants need to submit an application form for the permit (the form is available at the regional immigration bureau) and to present their passport, alien registration card (original or copy), and student ID card (if available at the time of the application).
The application is free of charge.
 
How to find part-time work
The following resources are available for foreign students who are looking for a part-time job:
Student affairs office at universities and schools
Employment magazines and newspaper ads

Job magazines: "TOWNWORK," "an," "DOMO!"
Community papers for foreigners:
"Metropolis" (distributed in Tokyo, Chiba, Kanagawa, Saitama),
"Tokyo Notice Board" (distributed in Tokyo and Kanagawa)
"Kansai Flea Market" (distributed in Kansai area)
Public employment offices (Hello Work)
Circles of friends, classmates, acquaintances, etc.
Bulletin boards at schools

Job information websites
TOWNWORK net: http://townwork.net
From A  navi: http://froma.yahoo.co.jp
DOMO! NET: http://domonet.jp
an: http://weban.jp/
R810.com: http://www.r810.com/
B-cause.inc: http://www.b-cause.co.jp/05staff/info_partjob.html
Metropolis: http://metropolis.co.jp
Tokyo Notice Board (Tokyo and Kanagawa): http://www.tokyonoticeboard.co.jp/
Kansai Flea Market (Kansai area): http://www.kfm.to/

(source : studyjapan.go.jp)