Abstract: A replaceable adapter for an electric hand tool, which is an electric screw driver or the like, includes an adapter seat, a clutch cap, a drill bit socket set and a joining sleeve disposed at the front end of the electric hand tool. The adapter seat extends an inner sleeve to fit with a bearing and the bearing is fixedly attached with a rotating shaft. The inner sleeve receives a compression spring. An end of the rotating shaft is joined to the output shaft of the electric hand tool. The adapter seat provides an inner annular projection at the bottom thereof and is surrounded with balls. The clutch cap has a cylindrical head inserts into the inner sleeve against biasing force of the compression spring. The cylindrical head provides an outer annular projection at the top thereof for engaging with the inner projection. An annular inner recess is disposed next to the cylindrical head. A drill bit socket set is joined to another end of rotating shaft.