The present invention relates to a rotary device in which a drill for soil earthwork is rotatably mounted, wherein the drill comprises: a shaft part; a screw, formed along the outer circumferential surface of the shaft part, for earthwork and the transportation of soil generated by the earthwork; a rotary shaft, formed on the upper part of the shaft part; a connection socket, formed on the rotary shaft, for adjusting the length; and a fixed shaft part, formed on the lower part of the shaft part, for being inserted and rotated into the soil for earthwork. More specifically, the present invention relates to a portable power rotary device provided with a drill having earthwork and cut-off functions, wherein a pair of horizontal blades face each other on the connection part between the shaft part and the fixed shaft part; screws, formed in every other layer, are symmetrically and integrally connected to each other on the pair of horizontal blades, for transferring soil upwardly; cutting blades, which are symmetrical with each other, are inclined downwardly and integrally formed on the pair of horizontal blades; a plurality of vertical blades, formed to be spaced apart from each other at a predetermined distance, protrude vertically on the upper portion of the lower wing of the screw; and when performing earthwork, soil and tree roots are cut by the cutting blades, and soil lumps, transferred along the screw, are cut again by the vertical blades.