Abstract: Disclosed herein is a light amount adjustment apparatus, including: a light amount adjustment member; a rotatable magnet formed in a disk shape; a driving arm configured to be pivoted by rotation of the magnet to operate the light amount adjustment member; a core having a pair of confronting portions positioned so as to sandwich the magnet from an outer circumference side and a connecting portion configured to connect end portions of the confronting portions to each other; a coil through which one of the portions of the core extends; and a base member having the core attached to the base member and supporting the magnet for rotation on the base member. The base member has a plurality of attaching projections provided at least at two places of the base member for attaching the core to the base member. The attaching projections have a small projection for fitting with the core.