A slot calculation unit calculates a current slot number and stores it in a slot storage unit. When each of control tasks of a recognition processing portion, a vehicle speed calculation portion, a brake control portion, and a steering control portion is activated, a slot number at the time of output of an execution result used as input data is obtained from a task table storage unit, and it is determined whether a time constraint is violated based on a permissible slot number for the input data, stored in a constraint table storage unit. When an execution result of each control task is output, the stored current slot number is read, and it is determined whether a time constraint is violated based on a permissible slot number for the output of the execution result, stored in the constraint table storage unit.