A camera comprises a main mirror which is arranged to guide the light of an object to be photographed to a viewfinder optical system and to be movable to and from its finder-viewing position and its exposure position; a sub-mirror which is arranged to guide the object light to a focus detecting device and to be movable to and from its focus detecting position and its exposure position; a spring member which is arranged to urge the sub-mirror; and a change-over mechanism which is arranged to change the urging direction of the spring member according to the moving position of the the main mirror and also to restrict the position of the sub-mirror when the sub-mirror is in the focus detecting position.
