A double-ended needle assembly, as a medical device, is provided with: a double-ended needle having a tip-end needle tip and a base-end needle tip a support member which is attached to the spout of a syringe, seals the spout in a liquid tight manner while being attached thereto, has a needle insertion section that allows the base-end needle tip to be inserted, and supports the double-ended needle in a manner such that the double-ended needle can move along the axial direction thereof and a cover member which is secured in relation to the double-ended needle, covers the tip-end needle tip while being secured, and moves the double-ended needle. In the initial state, the tip-end needle tip is covered by the cover member and the base-end needle tip is not inserted into the needle insertion section. When the state is shifted from the initial state to a state in which the cover member moves in the base end direction along with the double-ended needle, the base-end needle tip of the double-ended needle is inserted into the needle insertion section. Then, the secured state of the cover member in relation to the double-ended needle is released, and the cover member can separate from the double-ended needle.
