PURPOSE: To provide a semiconductor aligner without exposing resist at the time of alignment or at the time of auto-focusing.

CONSTITUTION: This semiconductor aligner has (a) laser light source 10, (b) a second-harmonic-wave generator 20 comprising a nonlinear optical crystal element and an optical resonator, (c) a resonator-length control device 30, which controls the resonator length of the optical resonator so as to control the level of the intensity of the light emitted from the second-harmonic-wave generator 20, and (d) an optical projecting system 62. A TTL-type alignment detecting system 40 or an auto-focusing device is provided. (A) The high-intensity light emitted from the second-harmonic-wave generator 20 is used as the light source for the optical projecting system. (B) The low-intensity light emitted from the second-harmonic-wave generator 20 is used as the light source for the TTL-type alignment detecting system or as the light source of the auto-focusing device.