The power generated by a power generating means (1) of a power-generating type electronic clock is measured by a first power generating sensing means (101) and a second power generating sensing means (102). The power generation level required when the operation is changed from a normal mode to a power-saving mode and the power generation level required when the operation is changed from the power-saving mode back to the normal mode are made different to prevent the phenomenon that the operation changes frequently by imparting hysteresis characteristics to the power generation level which causes a change in the mode, thereby improving the power-saving effect.