Provided are a pulse wave signal analyzer and an analysis method capable of determining a state of atrial fibrillation. The analyzer comprises a pulse wave detection unit for non-invasively detecting a pulse wave signal according to heartbeat of a living body; a spectrum generation unit for generating a frequency spectrum by Fourier transforming signal detected by the pulse wave detection unit; and an atrial fibrillation detection unit for detecting a state of atrial fibrillation based on the frequency spectrum generated by the spectrum generation unit. The spectrum generation unit repeatedly performs Fourier transform of the pulse wave signal at a predetermined time frame while shifting the time frame in a range of 0.005 to 0.02 seconds. The analyzer further comprises a filter for filtering the signal detected by the pulse wave detection unit, and the spectrum generation unit generates the frequency spectrum from signal output from the filter.