A fault simulation system comprising: a simulation unit configured to execute a plurality of simulations including a simulation of an electronic control unit process and a simulation of a vehicle process and to generate travel information wherein the travel information includes a vehicle trajectory; characterised by an analysis unit that is configured to set a type of fault to the travel information received from the simulation unit wherein the analysis unit is configured to set, to the travel information about a target vehicle for simulation, positional information to cause the fault on the vehicle; a control unit that is configured to cause the simulation unit to perform a simulation when a fault is caused based on the travel information to which the occurrence of the fault is set, wherein the fault is an element fault including switchable resistance values (Ron, Roff) of an electronic component configuring an ECU; and an output unit that is configured to output an executed result of the simulation unit; wherein the simulation unit is formed of: a torque sensor process that accepts an input of steering torque from a driver process and detects the steering torque with an electrical signal; a microcomputer process that executes a program determining an assist torque amount based on the steering torque and calculating a required torque amount for a motor; a mixed signal circuit process, in which a mixed signal circuit has an analog element and a digital element combined, including a driver circuit that drives the motor based on an output signal in the microcomputer process, a monitor circuit that detects a drive electric current of the motor, and a power supply circuit that supplies electric power; an electric power assisted steering system process having at least one process of steering gear processes that convert a torque output of the motor into rack thrust; and a vehicle motion process that finds a vehicle behavior from an output in the EPS process based on the travel information. a simulation unit configured to execute a plurality of simulations including a simulation of an electronic control unit process and a simulation of a vehicle process and to generate travel information wherein the travel information includes a vehicle trajectory; characterised by an analysis unit that is configured to set a type of fault to the travel information received from the simulation unit wherein the analysis unit is configured to set, to the travel information about a target vehicle for simulation, positional information to cause the fault on the vehicle; a control unit that is configured to cause the simulation unit to perform a simulation when a fault is caused based on the travel information to which the occurrence of the fault is set, wherein the fault is an element fault including switchable resistance values (Ron, Roff) of an electronic component configuring an ECU; and an output unit that is configured to output an executed result of the simulation unit; wherein the simulation unit is formed of: a torque sensor process that accepts an input of steering torque from a driver process and detects the steering torque with an electrical signal; a microcomputer process that executes a program determining an assist torque amount based on the steering torque and calculating a required torque amount for a motor; a mixed signal circuit process, in which a mixed signal circuit has an analog element and a digital element combined, including a driver circuit that drives the motor based on an output signal in the microcomputer process, a monitor circuit that detects a drive electric current of the motor, and a power supply circuit that supplies electric power; an electric power assisted steering system process having at least one process of steering gear processes that convert a torque output of the motor into rack thrust; and a vehicle motion process that finds a vehicle behavior from an output in the EPS process based on the travel information. a torque sensor process that accepts an input of steering torque from a driver process and detects the steering torque with an electrical signal; a microcomputer process that executes a program determining an assist torque amount based on the steering torque and calculating a required torque amount for a motor; a mixed signal circuit process, in which a mixed signal circuit has an analog element and a digital element combined, including a driver circuit that drives the motor based on an output signal in the microcomputer process, a monitor circuit that detects a drive electric current of the motor, and a power supply circuit that supplies electric power; an electric power assisted steering system process having at least one process of steering gear processes that convert a torque output of the motor into rack thrust; and a vehicle motion process that finds a vehicle behavior from an output in the EPS process based on the travel information.