A biological signal analysis device includes: an acquiring unit configured to acquire biological signals of a measurement target; a trigger information acquiring unit configured to acquire, from a stimulator configured to apply stimuli to the measurement target, trigger information indicating times at which the stimuli are generated; and a signal processing unit configured to process the biological signals. The signal processing unit is configured to calculate biological information on the measurement target based on the biological signals, maintain only pieces of trigger information corresponding to times at which it is determined that biological signals of the measurement target are generated, from the calculated biological information, delete another piece of trigger information, and use an averaged waveform that is obtained by performing an averaging process on the biological signals that are generated in synchronization with the stimuli based on the pieces of remaining trigger information.