A multiple optical axis sensor according to an embodiment of the present invention includes: a light projecting unit which includes a plurality of light projecting elements; and a light receiving unit which includes a plurality of light receiving elements that face the plurality of light projecting elements and receive light from the light projecting elements, wherein: when the amount of received light measured by at least one light receiving element among the plurality of light receiving elements is equal to or smaller than a first level and exceeds a second level that is smaller than the first level, the light projecting unit or the light receiving unit may output a first alarm through a display provided in the light projecting unit or the light receiving unit; when the amount of received light is equal to or smaller than the second level and exceeds a third level that is smaller than the second level, the light projecting unit or the light receiving unit may output a first self-diagnosis signal, which represents a reduced light reception state, through an output line while outputting a second alarm through the display unit; and when the amount of received light is equal to or smaller than the third level, the light projecting unit or the light receiving unit may output a third alarm, which represents a light blocked state, through the display, and may output a second self-diagnosis signal, which represents the light blocked state, through the output line.
MULTIPLE OPTICAL AXIS SENSOR