The invention discloses an infrared sensor which comprises a sensor body, transparent glass, epoxy glue, a filter, a connecting pin, a circuit component, a field effect transistor, a sensor body, a base and a casing. According to the invention, the filter and the transparent glass are arranged on the top of the casing to reduce the influence of various external heat sources and light sources on the pyroelectric infrared sensor; in order to have higher sensitivity to infrared radiation in a certain wavelength range, the filter is arranged in the casing; in addition to allowing passing of infrared radiation in certain wavelength ranges, the filter can reject light, sunlight and other infrared radiation; in addition, the field effect transistor is arranged in the casing, and the field effecttransistor has the advantages of high input resistance, low noise, low power consumption, large dynamic range, easy integration, no secondary breakdown, wide safe working area and the like; a detection signal can be amplified; the performance is stable; the accuracy of the signal is improved; a desiccant is arranged inside the casing to prevent moisture inside the casing; and the service life of the product is improved.