This paper presents a thermoelectric infrared (IR) sensor which comprise of an infrared detector and a readout circuitry. It is designed by TSMC 0.35 μm CMOS process with subsequent micromachining technology. The presented infrared sensing device can achieve the responsivity of 1277.92 V/W and time constant of 2.63 ms. The instrumentation amplifier (IA) for thermoelectric infrared sensor features a gain of 45.55 dB and a CMRR of more than 90 dB. The operation amplifier (op-amp) for IA realization has a gain of 70.45 dB with an 85 MHz bandwidth and a common-mode rejection ratio (CMRR) of more than 70 dB. The total power dissipation of readout circuit is 11.1 mW and the chip size is 1025×815 μm2.