A manipulation input device comprising: a projection component configured to project an image on a projection surface by scanning light from a light source; a photodetector configured to detect as scattered light the light reflected by a manipulation object; and an inclination determination component configured to acquire, for a plurality of scan lines of the light, position information of the manipulation object that is specified based on scanning angle information when the photodetector has detected the scattered light, and width information of the manipulation object that corresponds to a continuous detection duration during which the photodetector continuously detects the scattered light, characterized in that the inclination determination component is further configured to determine inclination of the manipulation object based on at least one of a temporal change in a plurality of sets of the width information and a temporal change in a plurality of sets of the position information, the projection component is further configured to project the image on the projection surface by alternately scanning the light in a main scanning direction that is perpendicular to a projection direction of the light, and in a sub-scanning direction that is perpendicular to the main scanning direction, and the inclination determination component is further configured to determine the inclination of the manipulation object in the sub-scanning direction according to a change rate in the plurality of sets of the width information with respect to a change in the scan lines and/or determine the inclination of the manipulation object in the main scanning direction according to a change rate in the plurality of sets of the position information with respect to a change in the scan lines. a projection component configured to project an image on a projection surface by scanning light from a light source; a photodetector configured to detect as scattered light the light reflected by a manipulation object; and an inclination determination component configured to acquire, for a plurality of scan lines of the light, position information of the manipulation object that is specified based on scanning angle information when the photodetector has detected the scattered light, and width information of the manipulation object that corresponds to a continuous detection duration during which the photodetector continuously detects the scattered light, position information of the manipulation object that is specified based on scanning angle information when the photodetector has detected the scattered light, and width information of the manipulation object that corresponds to a continuous detection duration during which the photodetector continuously detects the scattered light, characterized in that the inclination determination component is further configured to determine inclination of the manipulation object based on at least one of a temporal change in a plurality of sets of the width information and a temporal change in a plurality of sets of the position information, the projection component is further configured to project the image on the projection surface by alternately scanning the light in a main scanning direction that is perpendicular to a projection direction of the light, and in a sub-scanning direction that is perpendicular to the main scanning direction, and the inclination determination component is further configured to determine the inclination of the manipulation object in the sub-scanning direction according to a change rate in the plurality of sets of the width information with respect to a change in the scan lines and/or determine the inclination of the manipulation object in the main scanning direction according to a change rate in the plurality of sets of the position information with respect to a change in the scan lines.