A biological state estimating apparatus (1) includes a pair of electrocardiographic electrodes (11 and 12), a photoplethysmographic sensor (20), a peak detecting section (316 or 326), a pulse transmission time measuring section (330), a correlation information storing section (341), and a biological state estimating section (360). The electrocardiographic electrodes (11 and 12) detect an electrocardiogram signal. The photoplethysmographic sensor (20), which has a light-emitting element (21) and a light-receiving element (22), detects a photoplethysmogram signal. The peak detecting section (316 or 326) detects a peak of the electrocardiogram signal and a peak of the photoplethysmogram signal. The pulse transmission time measuring section (330) determines a pulse transmission time from the time difference between the peak of the photoplethysmogram signal and the peak of the electrocardiogram signal. The correlation information storing section (341) stores correlation information that is determined in advance on the basis of the relationship between pulse transmission time and biological state. The biological state estimating section (360) estimates the biological state of the user on the basis of the pulse transmission time, and the correlation information stored in the correlation information storing section (341).
