<p>Objective: The stability of the microcatheter is important in safe coil deployment. However, quantitative information regarding the relationship between the microcatheter shape and stability is limited. We investigated deformation characteristics of the microcatheter by applying loads to the tip of a placed microcatheter using numerical analysis.</p><p>Materials and Methods: Microcatheter models were prepared by connecting cylindrical rigid segments with coil springs. Four types of models with shapes mimicking parts of a blood vessel and three types of models with shapes that come into contact with the vascular wall on the opposite side of the aneurysm were prepared.</p><p>Results: When the distance between the tip of the microcatheter and the position of its contact with the vascular wall exceeded 12 mm, the suppressive effect on displacement of the microcatheter tip was markedly reduced. When this distance was less than 6 mm, the microcatheter shape exerted a greater effect on the stability than the distance.</p><p>Conclusion: These results suggest that not only the position of contact of the microcatheter with the vascular wall but also the shape of the microcatheter near the aneurysm plays an important role in securing the stability.</p>