The vegetable has the prices varying greatly depending upon the quantity supplied because it is a sort of necessities having low storage so that its demand is inflexible to the price. On the other hand, the supply of vegetable is said to be flexible to the price of the preceding term, so that farmers tend to increase cultivation areas greatly in current year when the price of previous year is high, and vice versa. Such characteristics of the supply have influence upon more fluctuation of yearly price of the vegetable in connection with those of the demand. Under such an uncertain situation, vegetable managers usually forecast and estimate how much they can accomplish yields and earnings and pay expenses prior to production. Based on the estimation, they make decision on the production. The paper estimated a variety of expected values and correlations that the managers can make decision by using the Monte-Carlo simulation.