If you are a citizen of a member state of the European Union, you are authorized to carry out paid work in Spain.

In the case of other nationalities, your study visa permits you to work for up to 20 hours a week, provided that your workday is compatible with your study or research commitments. Below is a translation of the article 90 from the 2000 Act on the rights and freedoms of foreign nationals in Spain:

Employment of students and researchers.

• Foreign students in possession of a student visa may be authorized to take on paid work, in public or private institutions, when the employer applies for a work permit and when all requisites listed under article 50, except for paragraphs a) and f), are met. The aforementioned activities must be compatible with the studies undertaken, and the income received must not be considered as the main means of support. It will not be necessary to apply for authorization for work placements in public or private institutions which form part of the study programme for which the student visa was granted, and which take place within the framework of the corresponding collaboration agreements between these institutions and the study centre in question.

• The contracts must be formalized in writing, and must be part-time contracts. In the event that the job requires the student to work a full working-day, its duration must not exceed three months, nor coincide with periods during which classes are given.
  
  

• The authorization granted will not be limited geographically, unless the paid activity coincides with periods during which classes are given; in this case, its location will be limited to the student’s area of residence for which the visa was issued.

• The validity of the authorization will be the same as the duration of the work contract, and may not exceed the duration of the visa or authorization of studies. When the visa expires, the authorization to work shall become void. Authorizations to work will be renewed if the circumstances that justified the previous approval still apply, provided that permission for the study or research stay has been duly renewed.
  
  

For more information, please consult the website of the Ministry of the Interior.