Provided is a prefilled syringe comprising, 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 parameters: (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.
