A known accelerator apparatus controls an acceleration state of a vehicle (e.g., an automobile) according to the amount of depression of an accelerator pedal, which is depressed by a foot of a driver of the vehicle.  In the accelerator apparatus, a rotational angle of a shaft, which corresponds to a rotational angle of a pedal arm connected to the accelerator pedal, is sensed.  In the vehicle, an opening degree of a throttle valve, which adjusts a quantity of intake air drawn into an internal combustion engine of the vehicle, is determined based on the sensed rotational angle.  A return mechanism and a hysteresis mechanism are received in an interior space of a support member of the accelerator apparatus.  The return mechanism urges the shaft in an accelerator-closing direction.  The hysteresis mechanism makes a pedal force, which is applied to the accelerator pedal at the time of depressing the accelerator pedal, to be larger than a pedal force, which is applied to the accelerator pedal at the time of releasing the accelerator pedal.  For instance, JP2007-253869A teaches the accelerator pedal apparatus, which has the hysteresis mechanism received in the interior space of the support member. 
However, in the accelerator apparatus of JP2007-253869A, a communication passage, which communicates between the interior space and an exterior space of the support member and corresponds to a movable range of the pedal arm, is formed.  When a foreign object enters into the interior space of the support member through the communication passage, the foreign object may possibly be caught at, for example, the return mechanism to result in malfunction of the accelerator apparatus.