A position detecting switch fixture for cylinder, having a pair of clamping reinforced plates at both ends of a mounting band, and clamping/holding a position detecting switch between these plates by a clamping screw. A holder is installed between the pair of clamping reinforced plates to clamp the position detecting switch. The clamping screw has the following clamping positions: a first clamping position where, due to the clamping of the pair of clamping reinforced plates, the base ends of the clamping reinforced plates adjacent to a cylinder tube approach each other, whereby the mounting band is temporarily fixed to the cylinder tube but the switch is not fixed; a second clamping position where, due to subsequent clamping, the switch is fixed to the holder; and a third clamping position where, due to further clamping, clamping restriction sections provided in the holder abut against each other to restrict still further clamping.