PURPOSE: To prevent basic data from being erased by a careless misoperation by, sequentially flickering plural indexes one by one and instructing a resetting operation.

CONSTITUTION: At a resetting mode, first segments 31 becoming the upper lateral lines on respective numeral display elements 19 arranged so as to constitute a numeral display part 11 are lighted and they are set to be the indexes of 'ON'. Fourth segments 34 becoming lower lateral lines are lighted and they are set to be the indexes of 'OFF'. At first, the lowest index is flickered and the 'ON' or 'OFF' of a resetting switch based on the index is continued. The index of the element 19 arranged in a next digit position is flickered, and the 'ON' or 'OFF' state of a resetting switch which is matched with the 'ON' or 'OFF' of the resetting switch shown by the index is continued. The flickering places of the indexes are sequentially moved. When the continuity of the on-state of the resetting switch and that of the off-state are repeated for the prescribed number of times, an accumulation value is set to be zero and basic data is cleared.