The invention relates to a washing device, in particular to an expressway guardrail washing device. Grooved wheels are arranged on two sets of wheel stands, the outer layer of a round-pole shape center pole is sleeved with a hairbrush shaft, a hairbrush is arranged on the surface of the hairbrush shaft, and flat-shaped nozzles are arranged in water injection nozzles of a front water injection stand and a back water injection stand; a front wheel rod is arranged on the center of the bottom face of the front water injection stand, a pressure relief spring is arranged on the rod bottom of the front wheel rod in a connected mode, the top face of a front guide roller is fixedly connected with the bottom end of the pressure relief spring, and a plurality of torsion springs are arranged on the bottom face of a back rack rod; hairbrush rods are arranged on spring heads of the torsion springs in a connected mode, a banister brush is arranged on the bottom face of a movable platform, a back guide roller is arranged on the bottom end of a back wheel rod, and a motor is arranged on the platform face of a support platform; according to the expressway guardrail washing device, a guardrail body is used as a guide rail, when the device is working, the washing device can be placed on a guardrail directly, the motor drives the hairbrush shaft and guide rail wheels to rotate and automatic cleaning is conducted, and the problems of low efficiency and high risk of manual cleaning and high cost, large size and complex device of a cleaning tanker can be avoided.