An API selection system that selects an API (Application Programming Interfaces) includes an API repository that accumulates an API in association with a functional requirement of the API, a save processing unit that receives, from an application developer, an input of an API request definition that defines the functional requirement and a non-functional requirement required for an API with which an application developed by the application developer is linked and saves the input in a storage unit, and a candidate API extraction processing unit that executes a candidate API extraction process of extracting, from the API repository, a plurality of candidate APIs having a functional requirement which matches or is similar to a functional requirement of the API request definition saved in the storage unit by the save processing unit.