The present invention aims at offering: a syringe connectable to a port in a fixed manner as well as capable of demonstrating high operational performance even in the case of direct connection where a connector is not used a connector used for the syringe and a syringe able to attach the connector thereto. For the attainment of the above objectives, the medical syringe of the present invention is a medical syringe including a cyrindrical connection supporting member which enhances the holding force of a luer part inserted into a port when the medical syringe is connected to the port. The connection supporting member is set by sliding along the luer or a syringe body in a state of being movable between a first position near a tip of the luer and a second position away from the tip of the luer. The medical syringe is characterized in that, when the connection supporting member is moved to the second position, the tip of the luer part is exposed.
