An operation amount detection apparatus includes a transmission member that transmits a load corresponding to an operation amount between a shaft portion and an operation target member through connecting portions that connect a first support portion supported by the operation target member and a second support portion supported by the shaft portion, and a detection device that detects an operation amount based on an amount of deformation of the connecting portions. A plurality of the connecting portions are provided in parallel between the first support portion and the second support portion, and deflect due to transmission of a load so that the first support portion and the second support are relatively displaced in a direction of a linear motion. The respective connecting portions are mutually opposed in a direction perpendicular to a lengthwise direction of the shaft portion.