A system for detecting a target object comprising: a radio wave sensor (211, 511) that is configured to emit radio waves and to detect reflected waves that are the emitted radio waves reflected by a target object; a thermal image sensor (221, 521) that is configured to detect heat generated by the target object; and an information collector that is configured to determine, on the basis of the detected reflected waves and the detected heat, whether the target object is present, wherein the information collector is configured to acquire, from the radio wave sensor (211, 511), detected information, while the thermal image sensor (221, 521) is OFF, and the information collector is configured to determine whether the radio wave sensor (211, 511) has detected the target object, while the thermal image sensor (221, 521) is OFF, characterized in that the information collector is configured to turn ON the thermal image sensor (221, 521) and to acquire, from the thermal image sensor (221, 521) detected information, only when the information collector determined that the radio wave sensor (211, 511) has not detected the target object, wherein the information collector is configured to keep the thermal image sensor (221, 521) OFF when the information collector determined that the radio wave sensor (211, 511) has detected the target object, the information collector is configured to determine whether the thermal image sensor (221, 521) has detected the target object after the information collector determined that the radio wave sensor (211, 511) has not detected the target object, wherein the radio wave sensor (211, 511) remains ON when the thermal image sensor (221, 521) is turned ON. a radio wave sensor (211, 511) that is configured to emit radio waves and to detect reflected waves that are the emitted radio waves reflected by a target object; a thermal image sensor (221, 521) that is configured to detect heat generated by the target object; and an information collector that is configured to determine, on the basis of the detected reflected waves and the detected heat, whether the target object is present, wherein the information collector is configured to acquire, from the radio wave sensor (211, 511), detected information, while the thermal image sensor (221, 521) is OFF, and the information collector is configured to determine whether the radio wave sensor (211, 511) has detected the target object, while the thermal image sensor (221, 521) is OFF, characterized in that the information collector is configured to turn ON the thermal image sensor (221, 521) and to acquire, from the thermal image sensor (221, 521) detected information, only when the information collector determined that the radio wave sensor (211, 511) has not detected the target object, wherein the information collector is configured to keep the thermal image sensor (221, 521) OFF when the information collector determined that the radio wave sensor (211, 511) has detected the target object, the information collector is configured to determine whether the thermal image sensor (221, 521) has detected the target object after the information collector determined that the radio wave sensor (211, 511) has not detected the target object, wherein the radio wave sensor (211, 511) remains ON when the thermal image sensor (221, 521) is turned ON.