To obtain an elastomer composition capable of preventing generation of adhesive wear, constructing an excellent transmission belt by including specific amount of constituents such as sulfur modified chloroprene rubber or the like and arranging Taber's abrasion resistance test value lower than a specific value.

This composition exhibits reaching to 40 mg of weight change under 500 g of load, 500 times of slipping after Taber's abrasion resistance test in conformity with JIS K 6264 by using a sand paper having ≤20 μm particle size, and includes (A) the sulfur modified chloroprene rubber, (B) a vulcanization accelerator, (C) zinc oxide and (D) magnesium oxide, the compounding amount of the component B is 0.1-5 pts to 100 pts.wt. of the component A, the compounding amount M1 of the component C and the compounding amount M2 of the component D preferably satisfies the formula using the Mooney scorch time (t35 at ML 125°C).