A signal detecting circuit of an infrared sensor includes: a cell array in which bolometers sensing infrared rays and outputting signal currents are arranged in an N×M format; a level generator that outputs a plurality of bias voltages corresponding to a plurality of bias levels; N resistor non-uniformity correcting circuits that are located in a column direction of the cell array and supply different bias voltages to each of the bolometers; M resistor non-uniformity correcting circuits that are located in a row direction of the cell array and supply different bias voltages to each of the bolometers; a control unit that sets a bias voltage level of each resistor non-uniformity correcting circuit to correct the resistor non-uniformity of the cell array; and N integrators that integrate the signal currents output from the cell array.