There is provided an automatic train operation system which can stop a train precisely at a stop target position without worsening ride quality even with the control system being a discrete system. The automatic train operation system comprises a relative distance measuring device to acquire information about a relative distance of the train relative to a stop position of a station to output average distance information that is the average of relative distances and a brake control device. The brake control device includes a sensor information holding unit to hold speed information and position information detected by sensors to output; a correction amount computing unit to compute a specifying value correction amount to output; and an instruction planning unit to compute a deceleration specifying value based on the specifying value correction amount and sensor information.