1. A three-dimensional image measuring device comprising: a hologram adapted for single exposure such that when reproduced, parallel light having a predetermined incident angle is irradiated, a plane light image is formed at a position located at a predetermined distance from the hologram in a depth direction; a light source for irradiating reproduced light on the hologram; parallel light converting means for converting the light from the light source into parallel light and irradiating the parallel light at the predetermined incident angle to the hologram; hologram moving and scanning means for imaging the parallel light image at a plurality of different positions extending in the moving and scanning direction by moving and scanning the hologram in a predetermined direction in such a manner that an angle between the parallel light and the hologram is kept at the predetermined incident angle; an object adapted to be measured being disposed in a space where the plane light image is formed; light receiving means including a plurality of two-dimensional-arranged light receiving elements for sequentially measuring the strength of scattered light of the plane light image imaged on a surface of the object as the hologram is moved by the hologram moving and scanning means; and distance measuring means for measuring the distance to the object based on an output of each light receiving element of the light receiving means.