A thermoplastic resin composition comprising a thermoplastic resin containing in a specific proportion a polyhydric alcohol which has 6 or more carbon atoms and in which the ratio of the number of carbon atoms to the number of hydroxyl groups is 1.5 to 30. The thermoplastic resin gives a 3 mm-thick molding having a haze of 10% or lower, a total light transmittance of 80% or higher, and a water absorption as determined through 100-hour immersion in 23 °C water of 0.1 % or lower, and has a glass transition temperature of 10 °C or higher and an aromatic ring content of 20 wt.% or lower. The resin is one selected among cycloolefin polymers, polycyclohexane resins, and 4-methyl-1-pentene polymers. The composition not only is excellent in transparency, heat resistance, mechanical properties, moisture-proofing properties, etc. and reduced in birefringence, but can retain its transparency even when environmental conditions change. Therefore, it is suitable for use as plastic lenses, optical recording media, containers, transparent sheets, transparent boards, etc.