In a contactless tonometer having a mechanism of puffing compressed air by moving a piston in a cylinder, puffing of unnecessary air against the eye to be inspected is suppressed. An apparatus includes a corneal shape changing unit configured to change a shape of a cornea of an eye to be inspected by compressing air in a cylinder by using a piston, and puffing the compressed air from the nozzle to the cornea, a piston control unit configured to control operation of the piston, and an intraocular pressure measurement unit configured to measure an intraocular pressure of the eye by detecting a state of a changed shape of the cornea. This apparatus includes a piston volume changing unit configured to change an initial volume when the piston compresses the air in the cylinder.
