The structure of the clean Ge(001) surface is locally and reversibly changed between c(4×2) and p(2×2) by controlling the bias voltage of a scanning tunneling microscope (STM) below 80 K. It shows hysteresis for the direction of the sample bias voltage change. The c(4×2) structure is observed with a sample bias voltage V_b ≤ −0.7 V. This structure is maintained at V_b ≤ 0.7 V with increasing the bias voltage. When V_b is higher than 0.8 V, the structure changed to p(2×2). This structure is then maintained at V_b ≥ −0.6 V with decreasing the bias voltage. The area of the structure change can be confined in the single dimer row under the STM tip using a bias voltage pulse. The observed local change of the reconstruction is attributed to the energy transfer process from the tunneling electron to the Ge lattice in the local electric field due to the STM bias voltage. A phenomenological model is proposed for the structure changes.