A prefilled syringe is provided that has high heat resistance, low adsorbability, low moisture permeability and low oxygen permeability.A prefilled syringe containing, as a resin constituting at least a barrel and a joint, a polyester resin that contains a diol unit having a cyclic acetal skeleton in an amount of from 1 to 30% by mol based on diol units and a dicarboxylic acid unit having a naphthalene skeleton in an amount of 70% by mol or more based on dicarboxylic acid units, and satisfies the following (i) to (iii):(i) a glass transition temperature of 110°C or more measured with a differential scanning calorimeter,(ii) a moisture permeation coefficient of 1 g·mm/m2/day or less, and(iii) an oxygen permeation coefficient of 10 cc·mm/m2/day/atm or less.
