In Infra-Red (IR) microscopy, the improvement of spatial resolution is difficult due to the diffraction limit of IR objective. As one of solutions, a solid immersion lens (SIL) is incorporated into the conventional objective. The high refractive index of SIL contributes to obtain the high spatial resolution image of sample immersed in SIL. However, the alignment between the SIL and the objective is difficult by the narrow depth of focus and field of view. In addition, the distance between the SIL and a sample should be less than 100 nm. Therefore the mounting device specialized for mounting of the SIL should be needed. In our study, we designed the mounting device to achieve of the maximum optical performance of the SIL. Vertical flexibility of the mounting device relieves limit of the movement in vertical direction and the contact stress. The mechanical safety and motion of the mounting device with the SIL were analyzed using finite element analysis. To evaluate the imaging system overall, the SIL was incorporated into the IR imaging system using the mounting device. As a result, we achieved the spatial resolution of $1.23{mu}m$ using obtained images of USAF target.