The present invention discloses a laser-aiming device for a radiant thermometer, which comprises a laser adjustment seat, a laser device, and a prism having two inclined faces. The laser adjustment seat is arranged on a temperature detection device of the radiant thermometer. The laser device and the prism are arranged on the laser adjustment device. The laser device generates a laser beam. The prism is located at the illuminated side of the laser beam and coaxial with the laser device, refracting the laser beam into two laser beams that generate two laser spots designating the detectable area of the radiant thermometer.