A micropump check valve device which can be designed thin with good assemblability and applied with urging force. The micropump check valve device includes an upstream side member having a small-bore hole for passing therethrough a fluid, a downstream side member having a large-bore hole for passing therethrough the fluid, and a valve member having a valve mechanism sandwiched between the upstream side member and the downstream side member. The valve mechanism includes a passing hole formed in correspondence to a position and a size of the large-bore hole in the downstream side member, a contacting part formed inside the passing hole in correspondence to the position and size of the small-bore hole in the upstream side member thereby to close the small-bore hole, and supporting parts formed to bridge across the passing hole to support the contacting part. The valve member has a greater linear expansion coefficient than the upstream side and downstream side members.