A surveillance system (1) includes an area information acquisition unit (101), a request information provision unit (102), and a participation consent reception unit (103). The area information acquisition unit (101) acquires information of a surveillance-desired area. The request information provision unit (102) provides participation request information for surveillance that is conducted by using an image capturing unit of a portable terminal in the surveillance-desired area. The participation consent reception unit (103) receives participation consent as a response to the participation request information, from the portable terminal.