The utility model discloses a segmental steam injection device of a horizontal well of an oil field. The segmental steam injection device is characterized by comprising an upper coupling, an upper joint, a sleeve, a spring baffle, a spring footstock, a conical ring, an oil pipe, a lower coupling, a spring and a small blocking ball with the diameter being greater than the diameter of the oil pipe, wherein the lower end of the upper coupling is connected to the upper joint, the lower end of the upper joint is arranged in the sleeve, the spring baffle is resisted against the bottom end of the upper joint, and the oil pipe is arranged in the spring baffle in a penetrating manner; the spring footstock is arranged on the inner lateral surface of the bottom of the sleeve, the oil pipe is arranged in an inner hole of the spring footstock in a penetrating manner, the conical ring is fixedly sleeved on the oil pipe at the lower part of the spring footstock, and is resisted against the spring footstock; the bottom of the oil pipe is fixedly connected to the lower coupling; the spring is resisted against the bottom surface of the spring baffle and the top surface of the spring footstock; the sleeve is provided with a plurality of steam holes in the sidewall between the bottom surface of the upper joint and the top surface of the spring footstock. According to the segmental steam injection device, the segmental steam injection of an oil layer is realized, the steam injection amount is reduced, and the steam injection cost is lowered.