Abstract
This is a study of Piaget's psychology for the applications to mathematics education. Theoretical analyses about the Operationalism and the child's conception of natural number in Piaget's psychology was intended to find out the implications for education. It was comprehended that the necessity to make appeal to the activities of children is founded on the mechanism of the intelligence. All actions of intelligence are operations and these operations are to function only in so far as to be prepared by the activities. In order to develop the conception of natural number in children, the activities about classes and order relations should be organized in the form of pre-curriculum according to the operational principle. Cuisenaire Rods is a good material for this purpose.
