A shape measurement instrument includes a plurality of transmitters 1 to 4 which radiate signals having different waveforms or phases, receivers 31 to 34 which receive signals reflected from an object O, correlation units 41 to 44 which obtain correlation waveforms between waveforms of the signals received by the receivers 31 to 34, and the signal radiated by a transmitter radiating the received signal of the transmitters 1 to 4, and a shape estimation unit 5 which extracts a quasi-wavefront based on the correlation waveforms obtained by the correlation units 41 to 44 and estimates a shape of the object O based on a relationship between the quasi-wavefront and the object O. As a result, a period of time required to measure an object shape can be significantly reduced.