To elucidate the dynamics of circulating tumor cell (CTC) in cancer metastasis, we propose an in vitro 3D model of capillary microconstriction. We developed a three-dimensional microfluidic device that has misconstructions with circular cross-section of 5 μm in diameter by combining photolithography technology and self-forming microbridge of an acrylic polymer solution, and successfully visualized cell transit through the microconstriction using cancer cells.