PROBLEM TO BE SOLVED: To provide a system in which, using a vehicle imaging device, a plurality of images of one vehicle are taken, and a speed is acquired from differential information of the images, while determining an advancing direction.SOLUTION: A traffic volume grasping device includes an imaging part for imaging a monitor region, control means for controlling the imaging part, and a frame memory for storing an image from the imaging part, for processing the image, so that type, passage, speed, and an advancing direction of a vehicle are detected. It includes means for reading a number plate of a vehicle with one or a plurality of images as a target image, means for particulating a type from the number plate, means for acquiring moving speed from a plurality of images having a time lag, and means for acquiring advancing direction of the vehicle from the plurality of images having a time lag.
