A laser scanning sensor comprising: a laser distance meter which emits a laser beam, and which measures a distance to at least one object present in a direction of the laser beam, based on a time until the laser beam reflects off the at least one object and returns to the laser distance meter; a scanning mechanism unit which changes a measurement direction by the laser distance meter; a distance information acquisition unit which defines a detection area and which sequentially acquires distance information containing at least one distance measured in each measurement direction in the detection area, by allowing the scanning mechanism unit to change the measurement direction and allowing the laser distance meter to make a periodic measurement; a detection area information storage unit which stores, as background distance information, a distance corresponding to an outer periphery of the detection area in each measurement direction; a first determination unit which determines that a reflecting surface is present, wherein the presence of the reflecting surface is determined when the distance information acquired by the distance information acquisition unit, in continuous measurement directions corresponding to a predetermined width or less, is greater by at least a predetermined distance than the background distance information in the respective measurement directions stored in the detection area information storage unit, and when this state changes thereafter by at least a predetermined rate in a predetermined time; a second determination unit which extracts a portion of the distance information that may correspond to a human body, the distance information having been acquired by the distance information acquisition unit, and which determines whether the extracted portion of the distance information corresponds to a human body, based on a sequential movement status regarding the extracted portion of the distance information; and a first alarm signal output unit which outputs a first alarm signal when the first determination unit has confirmed the presence of the reflecting surface or when the second determination unit has confirmed the presence of the human body. a laser distance meter which emits a laser beam, and which measures a distance to at least one object present in a direction of the laser beam, based on a time until the laser beam reflects off the at least one object and returns to the laser distance meter; a scanning mechanism unit which changes a measurement direction by the laser distance meter; a distance information acquisition unit which defines a detection area and which sequentially acquires distance information containing at least one distance measured in each measurement direction in the detection area, by allowing the scanning mechanism unit to change the measurement direction and allowing the laser distance meter to make a periodic measurement; a detection area information storage unit which stores, as background distance information, a distance corresponding to an outer periphery of the detection area in each measurement direction; a first determination unit which determines that a reflecting surface is present, wherein the presence of the reflecting surface is determined when the distance information acquired by the distance information acquisition unit, in continuous measurement directions corresponding to a predetermined width or less, is greater by at least a predetermined distance than the background distance information in the respective measurement directions stored in the detection area information storage unit, and when this state changes thereafter by at least a predetermined rate in a predetermined time; a second determination unit which extracts a portion of the distance information that may correspond to a human body, the distance information having been acquired by the distance information acquisition unit, and which determines whether the extracted portion of the distance information corresponds to a human body, based on a sequential movement status regarding the extracted portion of the distance information; and a first alarm signal output unit which outputs a first alarm signal when the first determination unit has confirmed the presence of the reflecting surface or when the second determination unit has confirmed the presence of the human body.