A substrate-floatation-type laser processing apparatus and a method for measuring a floating height, capable of improving performance of laser processing are provided. A substrate-floatation-type laser processing apparatus according to an embodiment includes a stage configured to float and convey a substrate, and a floating-height measurement apparatus configured to measure a floating height H of the substrate. Note that a distance between the floating-height measurement apparatus and the substrate can be automatically adjusted according to the measured floating height H. The floating height H of the substrate is measured by applying laser light to the substrate and the stage. The distance between the floating-height measurement apparatus and the substrate is adjusted by using a feedback mechanism in which the measured floating height of the substrate is used as an input.