A milk path cleaning device for a coffee machine, the device comprising: a stepping electric motor (1); a switching valve assembly, which is arranged in a cavity enclosed and defined by a left protection cover (2) and a right protection cover (3); a cleaning milk pipe (4); a cam slide block (5); a cam slide block fixing seat (6) slidably arranged in the cam slide block (5); a button (7); and a button detection device (8), wherein a pair of elastic clamps (18) are respectively arranged on two sides of the cam slide block (5), a spring B (19) for forcing the elastic clamp (18) to reset is arranged in each elastic clamp (18), and the button (7) is embedded in a vertical groove (51) at the upper end of the cam slide block (5), thereby pushing a button on the button detection device (8). A plug of a milk container is in clamp connection with the cam slide block (5), one end of the cleaning milk pipe (4) is connected to the switching valve assembly, and the other end of the cleaning milk pipe is connected to the plug of the milk container; and one end of a pair of cam connecting rods (17) is fixedly connected to the switching valve assembly, and the other end of the pair of cam connecting rods is slidably connected to the cam slide block (5). The fully automatic switching between a milk making loop and a milk cleaning loop can be realized, thereby achieving fully automatic milk making and fully automatic milk path cleaning.