To provide a tonometer by which a user can easily measure an ocular tension by himself.

A signal Qa starts ascending when a pressure sensor at the central part starts coming into contact with the pupil, and the ascending track changes at a pressure value Pa at that time in a stage when the cornea starts to be deformed, i.e., by a press-in amount Sa from a press-in amount Oa when the contact begins. In the meantime, a signal Qb starts ascending from a stage when a pressure sensor for the peripheral area starts coming into contact with the pupil, i.e., from a press-in amount Ob as a moving amount since the start of coming into contact with the pupil, and the ascending track changes at a pressure value Pb at that time in a stage when the cornea starts to be deformed, i.e., by a press-in amount Sb from a press-in amount Oa when the contact starts. Therefore, for the pressure at a specified deformed location of the cornea, the ocular tension is obtained by subtracting the pressure value Pb from a pressure value Pa' at the press-in amount Sb, which is a bending point for an output Qb of the pressure sensor for the peripheral area.