Provided are a biological-information detecting apparatus and a seat with a backrest capable of detecting biological information about a measurement subject with high accuracy while reducing burdens on the measurement subject in non-contact and non-retraining manner. According to the embodiment, the biological-information detecting apparatus includes first blood-flow measuring means 2 provided at a seat surface of a seat, the first blood-flow measuring means measuring a condition of a blood flow of a popliteal artery of a measurement subject seated in the seat, second blood-flow measuring means 3 provided at a back of the seat, the second blood-flow measuring means measuring a condition of a blood flow of a thoracic aorta of the measurement subject, and blood-pressure calculation means determining a pulse-wave propagation velocity and a degree of arteriosclerosis from blood flow data acquired by the first blood-flow measuring means 2 and blood flow data acquired by the second blood-flow measuring means 3 and calculating blood pressures of the popliteal artery and the thoracic aorta of the measurement subject based on the pulse-wave propagation velocity and the degree of arteriosclerosis.
