A prefilled syringe of a before-use mixing type is provided, which does not require a bypass portion defined by a recessed inner surface portion of an outer cylinder. In the prefilled syringe, a first gasket (4) and a second gasket (5) are fitted in the outer cylinder (2), and non-rotatively and complementarily shaped engagement portions (12), (13) are respectively provided at a front end of the first gasket (4) and a rear end of the second gasket (5) in order to reduce a liquid transfer period required for transferring a liquid between two chambers separated by the gaskets. During storage, the engagement portions (12), (13) abut against each other to be kept out of engagement with each other, whereby a drug containing space is defined between the gaskets (4), (5). When a liquid is transferred from a liquid containing space defined on a rear side of the first gasket (4) to the drug containing space, the internal pressure of the drug containing space is prevented from being excessively increased.
