An exemplary zoom ratio adjusting switch includes a panel, a rotary member and a spring. The panel defines first and second grooves whose innermost extremities are on a circumference of a circle. Each groove includes a wide part and a narrow part. The rotary member includes a body positioned to a top side of the panel and first and second locking legs extending from the body. The first and second locking legs extend though the wide parts and slide in the narrow parts respectively. Feet extend from the locking legs respectively at the bottom side of the panel and are restrained at the bottom side of the panel. The spring is positioned to the bottom side of the panel and restrains travel of the first locking leg from the narrow part to the wide part of the first groove.