Mass spectrometer

A mass spectrometer, comprising:

• a housing in which a vacuum chamber brought into a vacuum state at a time of analysis is formed, the housing having an opening communicating with the vacuum chamber;
• a door for opening and closing the opening, the door being attached in an openable and closable manner to a part of a wall surface that partitions the vacuum chamber in the housing;
• and
• a hinge portion configured to rotatably support the door between an open state and a closed state, wherein
• the door includes a closing portion that closes the opening in a closed state, and a holding portion that holds the closing portion and is connected to the hinge portion,
• the closing portion is connected to the holding portion on a side opposite to the hinge portion side, and is configured to be separable from the holding portion on the hinge portion side, and
• in a case where the door is rotated from an open state to a closed state, the closing portion is configured to come into contact with a peripheral edge portion of the opening on a side opposite to the hinge portion side before the closing portion comes into contact with a peripheral edge portion of the opening on the hinge portion side.