A displacement measuring method for measuring the displacement of the position of a measuring object in a displacement measuring direction, the method comprising: locating a target having a reflective part, where plural small reflective faces which are orthogonal to an impinging direction of a laser beam are formed with their positions shifted successively in the impinging direction so that reflected light is returned from the reflective part in a direction parallel with the impinging direction of the laser beam, at the position of the measuring object such that the displacement measuring direction is orthogonal a direction of the reflected light; and locating a laser rangefinder at a position which is relatively displaced in the displacement measuring direction relative to the measuring object position, characterized in that the displacement measuring method further comprises: making a laser beam projected from the laser rangefinder impinge orthogonally on the reflective faces, while a relation between a beam diameter of the laser beam and a dimension (Sa, Sb) of the respective small reflective faces is set such that the laser beam impinges on a plural number of the small reflective faces at the same time; with the laser rangefinder, receiving the reflected light returned from the small reflective faces on which the laser beam has impinged and determining a distance between the laser rangefinder and a laser beam reflecting position in the reflective part by said received reflected light; detecting a variation in the distance (Ls) from the laser rangefinder to the laser beam reflecting position; and measuring the displacement of the measuring object position in the displacement measuring direction by utilising correlation between the detected variation and the displacement of the measuring object position in the displacement measuring direction. locating a target having a reflective part, where plural small reflective faces which are orthogonal to an impinging direction of a laser beam are formed with their positions shifted successively in the impinging direction so that reflected light is returned from the reflective part in a direction parallel with the impinging direction of the laser beam, at the position of the measuring object such that the displacement measuring direction is orthogonal a direction of the reflected light; and locating a laser rangefinder at a position which is relatively displaced in the displacement measuring direction relative to the measuring object position, characterized in that the displacement measuring method further comprises: making a laser beam projected from the laser rangefinder impinge orthogonally on the reflective faces, while a relation between a beam diameter of the laser beam and a dimension (Sa, Sb) of the respective small reflective faces is set such that the laser beam impinges on a plural number of the small reflective faces at the same time; with the laser rangefinder, receiving the reflected light returned from the small reflective faces on which the laser beam has impinged and determining a distance between the laser rangefinder and a laser beam reflecting position in the reflective part by said received reflected light; detecting a variation in the distance (Ls) from the laser rangefinder to the laser beam reflecting position; and measuring the displacement of the measuring object position in the displacement measuring direction by utilising correlation between the detected variation and the displacement of the measuring object position in the displacement measuring direction. making a laser beam projected from the laser rangefinder impinge orthogonally on the reflective faces, while a relation between a beam diameter of the laser beam and a dimension (Sa, Sb) of the respective small reflective faces is set such that the laser beam impinges on a plural number of the small reflective faces at the same time; with the laser rangefinder, receiving the reflected light returned from the small reflective faces on which the laser beam has impinged and determining a distance between the laser rangefinder and a laser beam reflecting position in the reflective part by said received reflected light; detecting a variation in the distance (Ls) from the laser rangefinder to the laser beam reflecting position; and measuring the displacement of the measuring object position in the displacement measuring direction by utilising correlation between the detected variation and the displacement of the measuring object position in the displacement measuring direction.