An image pickup unit includes: a focus switching type observation optical system including fixed lenses and a moving lens; fixed frames that hold the fixed lenses; a moving frame that is arranged to be movable back and forth in a direction along a photographing optical axis of the observation optical system and holds the moving lens; and a correction frame fixed in the fixed frames, configured to house the moving frame such that the moving frame can advance and retract, including a stopper that abuts the moving frame to restrict movement in one direction of the photographing optical axis, and being slightly adjustable to realize one of focal lengths of the observation optical system.