PURPOSE: To prevent price data from being added moreover in a total memory when an addition key is pressed further, by calculating the price data, adding and storing the data in the total memory and clearing unit price data.

CONSTITUTION: Unit price data are set by a keyboard 2 (wherein a: price, b: erase, c: package, d: package, 2c: total addition, 2d: unit addition, 2e: change, 2f: unit subtraction, 2g: integration, 2h: total) and a quantity is measured by a measuring unit 1 to calculate the price. An addition key 2c is pressed to add and store price data in a total memory 8l and clear the unit price data. As a result, the price data are prevented from being added moreover in the total memory 8l when the addition key 2c is pressed further by erroneous operation.