To perform a measurement with highly reliable alignment by eliminating an occurrence of measurement error due to eclipse of a measurement light flux by the iris.

This refraction measuring instrument projects the light flux to the fundus oculi via the pupil of an eye to be examined, receives the light flux reflected from the fundus oculi and measures the refraction. This instrument is provided with an imaging means imaging the front eye part of the eye to be examined; a storage means storing the front eye part image taken by the imaging means; an operation distance detecting means detecting an operation distance between the eye to be examined and the instrument; a means of obtaining brightness information of a plurality of parts of storage pixels provided on the outermost circumference of an image area where the measurement light flux passes through among the stored front eye part image; and a determination means determining whether or not the measurement light flux can pass the pupil of the eye to be examined based on information obtained by the means of obtaining the brightness information.