The present invention enables a state in which two types of substances are in communication with each other via a double-ended needle assembly to be created by a one-step continuous pushing operation, while preventing an inflow of air or liquid leakage. This syringe device 1 is provided with an administration holder 2 and a cylinder portion 6 into which the administration holder 2 can be inserted. The cylinder portion 6 is provided with a connection holder 3, a slit holder 4 connected to the connection holder, and a double-ended needle assembly 5 disposed so as to be slidable in the connection holder 3. A cartridge for a freeze-dried product is loaded into the administration holder 2, while a cartridge for a solution is loaded into the connection holder 3. Once the administration holder 2 is pushed in, the double-ended needle assembly 5 slides. When one needle tip thereof has opened the cartridge for the freeze-dried product, the other needle tip of the double-ended needle assembly 5 slightly pierces the cartridge for the solution, and further sliding of the double-ended needle assembly 5 causes the other needle tip to open the cartridge for the solution.
