SMI (SPICA Mid-infrared Instrument) is one of the three focal-plane science instruments for SPICA. SMI is the Japanese-led instrument proposed and managed by a university consortium. SMI covers the wavelength range from 10 to 36 μm with four separate channels: the low-resolution (R = 60 - 160) spectroscopy function for 17 - 36 μm, the broad-band (R = 5) imaging function at 34 μm, the mid-resolution (R = 1400 - 2600) spectroscopy function for 18 - 36 μm, and the high-resolution (R = 29000) spectroscopy function for 10 - 18 μm. In this presentation, we will show the latest design and specifications of SMI as a result of feasibility studies.