The present invention provides a steering operation mechanism in which the life of a side brake friction plate is extended by stopping a lubricating oil from being retained and rising to a high temperature. Provided is a steering operation mechanism in which: a cylindrical sliding body to which a side gear is integrally molded is fit slidably around a steering operation shaft which is laid horizontally inside an oil bath lubrication-type transmission case； a multi-plate side brake is disposed in the outer periphery of the sliding body； and the sliding operation of the sliding body and the braking operation of the side brake are linked, enabling intermittent operation of power. A sliding body oil flow channel and brake oil flow channel, in which a lubricating oil flows in a radial direction of the steering operation shaft, are formed in the sliding body and side brake respectively, and the two oil flow channels are connected.
