Abstract: The invention provides a laser oscillator including (a) laser medium having a characteristic that distortion is caused in the laser medium by applying electric field thereto, (b) an optical pumping source for exciting the laser medium to thereby generate laser beam, (c) a pair of terminals through which a voltage is applied to the laser medium, and (d) an optical resonator including a total reflection coating attached to one of end surfaces of the laser medium and a partial reflection coating attached to the other of end surfaces of the laser medium. The laser oscillator provides advantages as follows: (a) laser outputs can be stabilized; (b) a laser oscillator can be small-sized; and (c) a laser apparatus can be also small-sized by incorporating the small-sized laser oscillator thereinto.