The purpose of this paper is to investigate the reason of double entry on the basis of the statement of receipts and disbursements. There are two types of the statement, type ① which shows cash receipts in debtor and cash payments in creditor, type ② which shows vice versa. To accomplish the purpose, this paper is constructed by two sections. Section 1 focuses on cash book from which the statement is prepared. Section 2 focuses on checking accuracy of cash balance which is calculated in cash book with the causes of cash receipts and payments, and tries to clarify the reason of double entry.