PURPOSE: To provide an excellent improved weatherability and provide a soft tennis ball whose surface crack generation is small and which has almost the same striking feeling and forming workability with those of a ball of natural rubber alone, by making the ball out of a rubber formation which contains by a specific rate EPDM whose iodine value is specific in regard to natural rubber.

CONSTITUTION: A soft tennis ball is made of a rubber formation which contains by 5-15wt.% EPDM whose iodine value is 10-15 in regard to natural rubber. When the iodine value of the EDPM is less than 10, the effect of crack prevention is small as vulcanization is insufficient, and when it is more than 15, vulcanization progresses too much, and the ball is hardened and the touch becomes rough, and even the feeling of ball-striking becomes affected. When an addition quantity is less than 5wt.%, it has no effect for crack prevention, and when it is more than 15wt.% it is effective against crack prevention, but the feeling of ball-striking becomes heavy with the increase of the addition quantity, and also the adhesiveness of the rubber combination lowers, so joining at the time of forming is not sufficient, and the outer appearance becomes bad, too. At the same time, there is a nonstandardization tendency such as a bound.