A biological information measurement apparatus includes a phase/frequency comparison unit that outputs a deviation signal based on a phase difference between a biological signal and an oscillation signal a variable loop filter that varies a cutoff frequency and a phase margin and that selectively blocks a signal of a predetermined frequency band contained in the deviation signal and a voltage controlled oscillation unit that generates the oscillation signal in accordance with the deviation signal that has passed through the variable loop filter. The apparatus further includes a CPU that estimates a SN ratio of the biological signal and analyzes a phase difference/frequency difference between the biological signal outputted from the comparison unit and the oscillation signal. The CPU further changes a constant of the variable loop filter based on the SN ratio and the phase difference/frequency difference.
