An API charging system comprising at least an API management device that is connected via a network to a plurality of platforms and manages APIs for each of a plurality of platforms, and a charging management device that manages charging for an application that uses the APIs via the network, wherein the API management device includes: a reception unit configured to receive selection of a charging condition when using an API from the application; a receiver configured to receive a request for usage of the API from the application; a transmitter configured to transmit a response according to the request to the application; and a history storage configured to store a history of the request for the API and the response for each of the applications that use the API, the charging management device includes: a charging condition storage configured to store the charging condition received by the reception unit for each of the applications that use the API when using the API; an acquisition unit configured to acquire information on the history from the history storage; and a determination unit configured to determine a charge value for the application that uses the API based on the charging condition and the information on the history, the determination unit determines a different charge value according to the charging condition for at least two of the applications that use the API and have the same history, characterized in that in a single application that uses a plurality of APIs among APIs for each of the platforms, a different charging condition is set for each of the APls, and the charging condition is flexibly set for each application for the API; the charging condition for one of the at least two of the applications that use the API and have the same history is according to a data amount in the request and a data amount in the response to the request; and the charging condition for the other of the at least two applications that use the API and have the same history is according to the number of requests. the API management device includes: a reception unit configured to receive selection of a charging condition when using an API from the application; a receiver configured to receive a request for usage of the API from the application; a transmitter configured to transmit a response according to the request to the application; and a history storage configured to store a history of the request for the API and the response for each of the applications that use the API, a reception unit configured to receive selection of a charging condition when using an API from the application; a receiver configured to receive a request for usage of the API from the application; a transmitter configured to transmit a response according to the request to the application; and a history storage configured to store a history of the request for the API and the response for each of the applications that use the API, the charging management device includes: a charging condition storage configured to store the charging condition received by the reception unit for each of the applications that use the API when using the API; an acquisition unit configured to acquire information on the history from the history storage; and a determination unit configured to determine a charge value for the application that uses the API based on the charging condition and the information on the history, the determination unit determines a different charge value according to the charging condition for at least two of the applications that use the API and have the same history, characterized in that a charging condition storage configured to store the charging condition received by the reception unit for each of the applications that use the API when using the API; an acquisition unit configured to acquire information on the history from the history storage; and a determination unit configured to determine a charge value for the application that uses the API based on the charging condition and the information on the history, the determination unit determines a different charge value according to the charging condition for at least two of the applications that use the API and have the same history, characterized in that in a single application that uses a plurality of APIs among APIs for each of the platforms, a different charging condition is set for each of the APls, and the charging condition is flexibly set for each application for the API; the charging condition for one of the at least two of the applications that use the API and have the same history is according to a data amount in the request and a data amount in the response to the request; and the charging condition for the other of the at least two applications that use the API and have the same history is according to the number of requests.