Mechanical device

A mechanical device comprising:

• a device main body having a housing chamber in which oil is stored;
• a plug attached to a bottom portion of the housing chamber in a state where an end of a shaft portion faces upward;
• a spacer member formed by a transparent member and arranged on the plug in such a manner that one end faces an inside of the housing chamber;
• at least one magnet body arranged on one end portion of the spacer member;
• and
• an image sensor arranged on the plug, the image sensor imaging the inside of the housing chamber via the spacer member, wherein
• the at least one magnet body is configured to maintain the state of adsorption of foreign matter made of a magnetic material, and
• the image sensor is configured to acquire the image data on which the foreign matter is displayed, via the spacer member.