A detection device for detecting a target behavior that is a vehicle behavior subjected to detection in a preset detection area using a laser radar that generates point cloud information by irradiating the detection area with laser light and receiving reflected light resulting from the irradiation with the laser light, the detection device comprising: an acquisition unit configured to acquire the point cloud information; a vehicle detection unit configured to detect a vehicle based on the point cloud information; and a behavior detection unit configured to detect the target behavior based on a direction of movement and an amount of movement per unit time of the vehicle detected by the vehicle detection unit, the target behavior being a traffic violation behavior, wherein the vehicle detection unit calculates position information indicating a position of the vehicle based on the point cloud information, characterized in that the behavior detection unit calculates a position vector indicating a distance and a direction from a second position indicated by second position information, which is the position information at time 2 before time 1, to a first position indicated by first position information which is the position information at the time 1, and divides the position vector by a time difference between the time 1 and the time 2 to calculate a velocity vector, the behavior detection unit calculates an inner product of the velocity vector and a reference vector which is preset in the behavior detection unit and which has an orientation along a permitted direction of traffic of the vehicle in the detection area, and compares the inner product with a predetermined threshold value to determine whether the vehicle has performed the target behavior, and the behavior detection unit outputs an acquisition command to cause an external device to acquire vehicle information that identifies the vehicle that has performed the target behavior. an acquisition unit configured to acquire the point cloud information; a vehicle detection unit configured to detect a vehicle based on the point cloud information; and a behavior detection unit configured to detect the target behavior based on a direction of movement and an amount of movement per unit time of the vehicle detected by the vehicle detection unit, the target behavior being a traffic violation behavior, wherein the vehicle detection unit calculates position information indicating a position of the vehicle based on the point cloud information, characterized in that the behavior detection unit calculates a position vector indicating a distance and a direction from a second position indicated by second position information, which is the position information at time 2 before time 1, to a first position indicated by first position information which is the position information at the time 1, and divides the position vector by a time difference between the time 1 and the time 2 to calculate a velocity vector, the behavior detection unit calculates an inner product of the velocity vector and a reference vector which is preset in the behavior detection unit and which has an orientation along a permitted direction of traffic of the vehicle in the detection area, and compares the inner product with a predetermined threshold value to determine whether the vehicle has performed the target behavior, and the behavior detection unit outputs an acquisition command to cause an external device to acquire vehicle information that identifies the vehicle that has performed the target behavior.