Case structure for fluid pressure device

A case structure for a fluid pressure device having a case into which a pressure fluid is introduced to an interior thereof, the fluid pressure device comprising:

• a body having ports through which the pressure fluid is supplied and discharged;
• and
• the case formed as a bottomed cylinder, which is connected to an installation hole of the body, the interior of the case communicating with the ports,
• wherein the case comprises a first case portion and a second case portion disposed in an interior of the first case portion, the first case portion being light-permeable around an entire circumference thereof so as to enable visibility of the second case portion and of the interior of the case, and the second case portion being light-permeable around an entire circumference thereof so as to enable visibility of the interior of the case, and
• wherein a first engagement member, which is disposed on an outer circumferential surface of at least one of the first case portion and the second case portion, engages with a second engagement member formed on an inner circumferential surface of the installation hole.