An operation input device includes: an operation body having a handle portion. The operation body tilting around a rotation center point when a user tilts the operation axis line of the handle portion. The operation body tilting in a predetermined number of tilting directions. The operation input device including multiple detection portions, the number of the detection portions being less than the predetermined number of tilting directions of the operation body. Each detection portion outputting a first output value when the operation body tilts in a direction corresponding to the detection portion and outputting a second output value when the operation body tilts in a direction not corresponding to the detection portion. A determination device determines a tilting direction of the operation body based on information on the number of first output values and information on a part of the detection portions that have outputted the first output values.