An image pickup apparatus capable of reducing variations in the time it takes for mirror bounce to end caused by adjustments made to the angle of a mirror, making assembly of the image pickup apparatus more efficient, and making the image pickup apparatus more compact. A mirror unit comes into contact with a positioning pin so as to be positioned in the shooting optical path. Rotating an adjustment member, on which a lock lever is rotatably fitted and to which the positioning pin is fixed, causes the mirror unit to move following the adjustment member. The lock lever and the positioning pin eccentrically move according to the rotation of the adjustment member and move in the same direction by the same amount. A gap between the mirror unit and a lock pin of the lock lever is constant.