Materials exhibiting giant magnetocaloric effect (i.e. the large temperature change under a magnetic field variation) are the most promising type for magnetic refrigeration. However, in order to gain from this giant effect, it is necessary for the material to show first order magnetic transition around room temperature. Some antiperovskite intermetallics Mn3AX (A= Ni, Cu, Zn, Ga, etc.; X=N, C) present isotropic volume contraction (first-order transition) accompanied by a magnetic transition, indicating the presence of strong magnetostructural coupling. Therefore, antiperovskites may be an appropriate playground to exploit magnetocaloric material. We recently found Mn3CoN might serve as a promising system for exploring MCE around room temperature. To reveal the magnetostructural coupling, we intend to conduct neutron diffraction.