The present invention discloses a crossroad traffic flow monitoring device. The device comprises a first monitoring frame assembly, a second monitoring frame assembly, a third monitoring frame assembly and a fourth monitoring frame assembly which are respectively installed at the north, east, south and west of a crossroad and are identical; each of the first monitoring frame assembly, the second monitoring frame assembly, the third monitoring frame assembly and the fourth monitoring frame assembly includes a first upright column assembly, a horizontal beam assembly, a first monitor, a second monitor, a third monitor, a fourth monitor, a fifth monitor, a sixth monitor, a second upright column assembly and a ground monitoring assembly; and a central controller is arranged next to the crossroad. Each monitor of the crossroad traffic flow monitoring device of the present invention only monitors the traffic condition of one lane, so that mutual interference can be avoided; the shooting angles of cameras can be changed from far to near, and therefore, the comprehensiveness of the acquisition of the image information of passing vehicles can be improved; the image information of the chassis of the vehicles can be recorded, and therefore, the intelligence of traffic flow statistics can be realized; and the statistics of the traffic flow information of different types of vehicles is additionally realized.