An injection device including a microneedle structure including a substrate having a first surface and a second surface opposite to the first surface, and a protrusion protruding from the first surface in a direction opposite to the second surface, the protrusion having a through hole which penetrates from a tip of the protrusion to the second surface in the direction of the protrusion such that a liquid flows through the through hole, and one or more check valves positioned to stop the liquid flowing from the second surface.