Spot shape detection apparatus

A spot shape detection apparatus for detecting a spot shape of a laser beam oscillated by a laser oscillator, the spot shape detection apparatus comprising:

• a focusing lens for focusing the laser beam oscillated by the laser oscillator;
• a rotary body in which a plurality of mirrors for reflecting the laser beam having passed through the focusing lens are disposed on concentric circles;
• a drive source for rotating the rotary body at a predetermined period;
• a beam splitter for branching return beams of the laser beam reflected by the plurality of mirrors of the rotary body;
• an imaging unit which is disposed in a direction in which the return beams are branched by the beam splitter and which images spot shapes of the return beams;
• and
• a display unit for displaying images obtained by imaging by the imaging unit, in relation with the plurality of mirrors,
• wherein the plurality of mirrors are disposed in the rotary body in such a manner that when the rotary body is rotated in a predetermined direction, focal points of the return beams of the laser beam reflected sequentially by the plurality of mirrors gradually approach an imaging position of the imaging unit, reach the imaging position and gradually come farther from the imaging position.