It is not difficult to be able to get a machined immersion grating in the market, and to obtain high spectrum-resolution (λ/Δλ > 200,000) in the middle infrared (3~5 micrometers) any longer. This wavelength region is a part of the molecule fingerprint region and is a very important wavelength region for the analysis of human / living activities. Compared with FT-IR in popular use, the spectrum by such classic device is an important means to a high-speed spectrum. However, although the dispersing potential of an immersion element is excellent, in offer of a device only, it does not mean in practical use for the researcher and the developer who want to use a high-performance spectroscope. So, in this paper, the high-resolution (λ/Δλ ~ 30,000 at 3-5 micrometer) spectrum unit which used Germanium (Ge) immersion grating is proposed. The optical plane size in this spectrum unit is about 200mm x 100mm, it is almost same as the iPad/mini4 (203.2mmx134.8mm) of the Apple Inc. It has fitted in less than 1/10 size compared with the reflected type spectroscope. This means dramatic improvement in the chance of an opportunity using a high-resolution spectroscope including ultrafast application. A large diversion is obtained in smaller beam size according to the refractive index of material in the immersion grating. In this paper, it introduces about the practical design of the high distribution immersion spectroscope. Especially, we introduce in detail about the manufacture of Ge immersion grating as the key device.