A walker comprises: a cross brace having an end sleeve on each end, N-shaped leg extensions, a lock body having a housing and a block having an axis hole, wherein the leg extension is covered by the end sleeve, the lock body is provided on top of the end sleeve, the leg extension and the lock body are provided with a pin hole and a connecting pin hole respectively at corresponding positions and fixed by a lock pin, the housing of the lock body is provided with a hole for sub axis, the block is connected inside the housing by a sub axis passing through the hole for sub axis and the axis hole, the end sleeve is provided with an orientation hole, a flange for fitting with the orientation hole is provided at the bottom of the block in the housing, a stretch part with a bearing rod is provided inside the leg extension, and the bearing rod leans against the upper portion of the block above the axis hole by passing through a through hole on the leg extension. The invention of this walker is of simple structure and assembly, easy processing and folding, light weight, convenient to transportation and storage. It meets of the demands of different users.