The invention discloses an energy-saving electric hole digger. A transmission shaft is driven by a motor, a sleeve and the transmission shaft are connected through a one-way ratchet wheel, a central one-way expansion drill bit is connected at the tail end of the transmission shaft, and spiral guide vanes are fixed on the transmission shaft and the sleeve. When the motor rotates forwards, the central one-way expansion drill bit and the sleeve break soil downwards, and broken soil is discharged by the spiral guide vanes to form a hollow cylindrical soil core; when the motor rotates reversely, the sleeve loses transmission of the one-way ratchet wheel, the central one-way expansion drill bit expands reversely and tightly clamps the soil core, and the soil core can be taken out. The energy-saving electric hole digger is good in soil breaking effect, low in soil breaking rate, energy saving, simple, portable, convenient to operate and suitable for various terrains.