Infrared spectrophotometer and method of storing window member

An infrared spectrophotometer that irradiates a sample in a sample chamber with infrared light and detects light from the sample with a detector, the infrared spectrophotometer comprising:

• a housing having a partition wall constituting a wall surface of the sample chamber, with an interferometer chamber in which an optical component is disposed being formed on an opposite side to the sample chamber with respect to the partition wall;
• a window member that is attachable to and detachable from an opening formed in the partition wall and transmits light between the sample chamber and the interferometer chamber;
• and
• a lid member attachable to and detachable from the window member and having a space formed internally,
• wherein the lid member engages with the window member attached to the opening from a side of the sample chamber so that the side of the sample chamber of the window member is covered with the lid member to set the space in a substantially airtight state.