PURPOSE: To obtain the subject composition improved in tension decay characteristics under high-temperature and high-humidity conditions, and to provide the a belt therefrom which can keep its tension load under high- temperature and high-humidity conditions for a long time without detriment to the tension decay characteristics at ordinary temperature.

CONSTITUTION: The body 1 of a conveying belt A is made from a millable urethane rubber composition prepared by mixing 100 pts.wt. millable polyurethane polymer with 1-10 pts.wt. DOP as a plasticizer of a boiling point of 360°C or above and 1-10 pts.wt. DBP as a plasticizer of a boiling point of below 360°C and is adapted so that its tension decay characteristics scarcely and apparently change under conditions varying from ordinary temperature ones to high-temperature and high-humidity ones.