A ratchet wrench applicable to multi-size workpieces comprises: a wrench with a handle and a head wherein the head has a hollow handle hole in which there are two neighboring surfaces along its inner edge, a first support surface and a second support surface, and an accommodating space embedded into the handle; a support portion with a ratchet part and a resilient member wherein the ratchet part allows one end to be pivoted in the accommodating space and is provided with an arc-convex portion, which is within the hollow handle hole for a first working space developed inside, and the resilient member always exerts a resilient resistance on the ratchet part. As such, the ratchet wrench depends on a simple mechanism and is applicable to continuous screw operation of various screw fastening elements for excellent convenience and swiftness.