Abstract: A single-beam photothermal measurement apparatus and a measurement method for absorptive defects. The apparatus comprises a common-path-type structure and a non-common-path-type structure. The present invention is simple in optical structure and convenient to align and adjustment. The measurement result is stable, and measurement signal anomalies caused by environmental vibration and sample tilt are avoided. By detecting a power change on the edge of a beam spot, the measurement sensitivity of a system is remarkably improved.