To provide an accelerator pedal device capable of reducing complicatedness of manufacturing processes, and improving precision related to detection of accelerator pedal depression action quantity.

A rotary shaft (main shaft) 20 of a pedal arm provided in this accelerator pedal device has a continuous form comprising plural columnar bodies (parts) of different outer diameters having a center axis P in common from an axial end 20a to a tip 20b and arranged from larger to smaller. In an outer circumference of a large diameter part 22, a pair of flat parts S1 (one flat part S1 only is shown in Fig.) are provided in parallel to each other from the boundary to a middle diameter 23 for a specified range L1 to form a double surface width. In an outer circumference of a middle diameter part 23, a pair of flat parts S2 (one flat part S2 only is shown in Fig.) are provided in parallel to each other from the boundary to a small diameter part 24 for a specified range L2 to form a double surface width similarlly.