The invention discloses a cornea-diameter optical measurement device. The cornea-diameter optical measurement device comprises a light source, a parallel crack light generation unit, an imaging unit,an adjusting unit and a display unit, wherein the light source provides a first illuminating beam and a second illuminating beam for the parallel crack light generation unit, and the parallel crack light generation unit comprises a first parallel crack light generation unit and a second parallel crack light generation unit; the first parallel crack light generation unit is used for generating first parallel crack light according to the first illuminating beam, and the second parallel crack light generation unit is used for generating second parallel crack light according to the second illuminating beam; the adjusting unit is used for adjusting relative positions between the first parallel crack light and the second parallel crack light and the cornea, and the cornea diameter is obtained through an interval between the first parallel crack light and the second parallel crack light. The cornea-diameter optical measurement device is non-contact, high in accuracy and efficiency and free ofside effect.