A proximity detection device configured to detect approach of a user to a display surface of a display, the proximity detection device comprising: a plurality of infrared light sources that is arranged outside and along a first side which is one side of the display surface of the display, and configured to emit infrared light passing through an area in front of the display surface diagonally; a plurality of photodetectors each arranged between two infrared light sources along the first side of the display surface; a proximity detection unit configured to detect the approach of the user to the display surface when an intensity which is detected by the photodetector corresponding to the infrared light source according to a predetermined positional correspondence and an intensity of reflection light of the infrared light emitted by the infrared light source is used as a first detection reflection intensity of emission light of the infrared light source for each of the plurality of infrared light sources and the intensity of the reflection light of the infrared light indicated by the first detection reflection intensity of the emission light of each infrared light source exceeds a set threshold value; and a threshold value setting unit configured to set a threshold value to the proximity detection unit such that the threshold value changes depending on an evaluation value calculated according to a predetermined evaluation function from each second detection reflection intensity and each first detection reflection intensity by using, as target infrared light sources, one or a plurality of infrared light sources of the plurality of infrared light sources and using, as second detection reflection intensities of emission light of the target infrared light sources, intensities which are intensities of reflection light of infrared light emitted by the target infrared light sources and are detected by the photodetectors further from the target infrared light sources than the photodetectors corresponding to the infrared light sources which are the target infrared light sources according to the correspondence for each target infrared light sources. a plurality of infrared light sources that is arranged outside and along a first side which is one side of the display surface of the display, and configured to emit infrared light passing through an area in front of the display surface diagonally; a plurality of photodetectors each arranged between two infrared light sources along the first side of the display surface; a proximity detection unit configured to detect the approach of the user to the display surface when an intensity which is detected by the photodetector corresponding to the infrared light source according to a predetermined positional correspondence and an intensity of reflection light of the infrared light emitted by the infrared light source is used as a first detection reflection intensity of emission light of the infrared light source for each of the plurality of infrared light sources and the intensity of the reflection light of the infrared light indicated by the first detection reflection intensity of the emission light of each infrared light source exceeds a set threshold value; and a threshold value setting unit configured to set a threshold value to the proximity detection unit such that the threshold value changes depending on an evaluation value calculated according to a predetermined evaluation function from each second detection reflection intensity and each first detection reflection intensity by using, as target infrared light sources, one or a plurality of infrared light sources of the plurality of infrared light sources and using, as second detection reflection intensities of emission light of the target infrared light sources, intensities which are intensities of reflection light of infrared light emitted by the target infrared light sources and are detected by the photodetectors further from the target infrared light sources than the photodetectors corresponding to the infrared light sources which are the target infrared light sources according to the correspondence for each target infrared light sources.