To perform a notification at an appropriate timing by highly accurately detecting a start of a stopped vehicle.

When an area of a region including grouped optical flow is a threshold or more, this start notification device notifies a driver of a start of a forward vehicle whose moving direction is indicated by the optical flow. When an area of a region including feature points uninvolved in the regulation of the optical flow is less than the threshold, this start notification device notifies of the start of the forward vehicle. This method can thus notify the start of the forward vehicle that is stopped in front thereof to the driver driving the vehicle at an appropriate timing.