An upper frame for an excavator is provided to smoothly transmit the load and shock which is transmitted through a mounting portion of a working device during operation (e.g., a lifting operation mode), to an upper frame by integrally installing a bracket for mounting a fuel tank or the like on an upper plate of the upper frame. The upper frame includes a center frame having a bottom plate and a pair of side plates and vertically welded to the bottom plate, a left side frame welded to the side plate of the center frame, a right side frame welded to the side plate of the center frame, an upper plate placed in the front of the center frame for supporting a bracket for a working device, to which a boom is pivotally secured, and an extended member integrally extended from one end of the upper plate for supporting desired parts.