A method of detecting a condensing spot position in a laser beam processing apparatus, including: a detection position setting step of setting a plurality of Z-axis directional positions in a range from a starting point to an ending point of detection positions into which the condenser is positioned; a laser beam processed groove forming step of sequentially positioning the condenser into the detection positions in the range from the starting point to the ending point, performing a predetermined interval indexing feeding by operating indexing feeding means each time the detection position for the condenser is changed, and forming a laser beam processed groove of a predetermined length in the plate-shaped body at each of the detection positions for the condenser; and a laser beam processed groove imaging step of imaging the laser beam processed grooves formed in the plate-shaped body by imaging means.