Image sending apparatus and authentication method in image sending apparatus

An image sending apparatus (200) includes a first authentication means for performing processing for first authentication to authenticate a user, a storage means (210) for storing authentication information (5000) used when the first authentication means authenticates the user, a sending means capable of sending image data by a plurality of kinds of sending methods, a destination setting means for setting a destination to which the sending means sends the image data, a second authentication means for performing processing for second authentication required for the sending means to send the image data to the destination set by the destination setting means, and a determination means configured to determine whether to use the authentication information (5000) stored in the storage means (210) when the second authentication means performs the processing for the second authentication, based on the sending method by which the sending means sends the image data to the destination.