To provide a system for detecting biological information capable of extracting a heart beat signal as biological information with high accuracy if an electric signal value from a sensor is changed.

A system 1 for detecting biological information includes: a pressure detecting means 10 for detecting a pressure showing biological information comprising a living body movement, a breath, and heart beat without contact and outputting the pressure signal of the living body; a threshold introducing means 20 for introducing the threshold for extracting a pressure signal of heart beat from a pressure signal of the living body; and a heart beat extracting means for extracting the pressure signal of heart beat from the pressure signal of the living body. The threshold introducing means 20 comprises a first filter part 21 with a large time constant for inputting the pressure signal 15a of the living body and smoothing and a second filter part 22 with a small time constant, a first operation part 23 for processing the smoothed signal which is output from the first and second filter parts 21 and 22 and introducing the minimum value 23a, and a second operation part 25 for introducing the thresholds 25a and 25b for extracting the heart beat signal of the living body by the minimum value 23a introduced by the first operation part 23.