A work machine includes: a first posture detection device which detects a posture of an upper slewing body with respect to a lower travelling body; a second posture detection device which detects a posture of a blade; a laser beam receiver which is provided to the upper slewing body and can receive a laser beam emitted from a laser beam emitter; and a calculation unit which calculates a height position of a cutting edge of the blade with respect to a surface to be constructed. The calculation unit calculates the height position of the cutting edge of the blade with respect to the surface to be constructed based on a laser beam receiving position where the laser beam is received by the laser beam receiver, a posture of the upper slewing body with respect to the lower travelling body, and a posture of the blade.