Seal state detecting device and seal state detecting method

A seal state detection device detecting a seal state of a seal member of a cylinder device including:

• a cylinder in which a working fluid is sealed;
• a rod protruding from at least one end of the cylinder to be extendable and contractible;
• and the seal member provided between the cylinder and the rod, the seal state detection device comprising:
• a plurality of part case members, wherein each of the part case members includes a cylinder facing part and a rod facing part and disposed to be aligned in a circumferential direction of the cylinder by causing the cylinder facing part to face the cylinder and the rod facing part to face the rod so that a housing chamber for housing a part of the cylinder and a part of the rod is formed between the cylinder facing part and the rod facing part, wherein each of the cylinder facing parts includes a seal part which comes into contact with the cylinder, the seal part includes a protruding part formed at one end and a recessed part formed at the other end in the circumferential direction of the cylinder, and the protruding parts and the recessed parts facing in the circumferential direction of the cylinder are fitted to each other when the plurality of part case members are disposed to be aligned in the circumferential direction of the cylinder.