An image pickup unit 30 includes: a focus switching type observation optical system 33 including fixed lenses 56a and 56b and a moving lens 66； fixed frames 55 and 57 that hold the fixed lenses 56a and 56b； a moving frame 65 that is arranged to be movable back and forth in a direction along a photographing optical axis O of the observation optical system 33 and holds the moving lens 66； and a correction frame 47 fixed in the fixed frames 55 and 57, configured to house the moving frame 65 such that the moving frame 65 can advance and retract, including a stopper 60 that abuts the moving frame 65 to restrict movement in one direction of the photographing optical axis O, and being slightly adjustable to realize one of focal lengths of the observation optical system 33.
