Magnetic mirrors exhibit predominant physical characteristics such as high surface impedance and strong near-field enhancement. However, there is no way to implement these materials on a silicon lab chip. Here, we propose a scheme for an in-plane magnetic mirror in a silicon-based photonic crystal with a high-impedance surface, in contrast to the previous electric mirrors with low surface impedance. A tortuous bending waveguide with zero-index core and magnetic mirror walls is designed that exhibits high transmission and zero phase change at the waveguide exit. This type of magnetic mirror opens the door to exploring the physics of high-impedance surfaces and applications in integrated photonics.