Provided is an electronically controlled throttle device for an engine driving to open and close a throttle valve (8) of a valve body (3) to which rotation of a motor (15) is transmitted from a driven gear (14) via a throttle shaft (6), and disposing a substrate (22) on which an excitation conductor (23) and a signal detection conductor (24) are arranged to face an exciting conductor (21) rotating together with the throttle shaft (6). The driven gear (14) comprises an embedded core metal (25), and has one side surface to which an exciting conductor (21) is exposed, the core metal (25) and the exciting conductor (21) being insert-Molded of a synthetic resin material and prepared, and a caulked portion (6a) of the throttle shaft (6) is inserted and fixed into a shaft hole (25a) extending through the core metal (25).