A detectable manipulation of accurately operating shaft input device, to provide a tilt direction determination method, and the tilt direction determination program. An input device 100 includes a base 121 which includes a connecting portion 141, an operating shaft 122 that includes a proximal end 151 connected to the connecting portion 141 and distal end 152, the base portion 121 corresponding to the operation of the operation shaft 122 and at least one detector group 135 detects the distortion comprises operating shaft 122 extends in a first direction from the proximal end 151 to the distal end 152, the operation shaft 122, at least one detection direction perpendicular to the first direction is supported tiltably base 121 toward each of the at least one detector group 135 corresponds to a different one of the at least one detection direction, each of the at least one detector group 135, the corresponding detection It includes three or more distortion detector 133 for detecting the distortion of the base portion 121 corresponding to the operation of the operating shaft 122 in the direction. .FIELD 6