The present invention provides a resin composition comprising (A) a polyethersulfone-based resin and (B) a compound having a weight reduction starting temperature determined in JIS K7120 of 150° C. or higher, a melting point of 100° C. or higher and a molecular weight of 500 or less, in a ratio (A):(B) within a range of from 100:5 to 100:1, in terms of a weight ratio. The polyethersulfone-based resin composition has high fluidity in a molten state and emit deduced smaller amounts of gas in processing. The molded article obtained from the composition also generate smaller amounts of gas discharged while being utilized.