To provide a mutually joining structure of unit type construction for joining living units with finishing of the inside/outside parts completed in a factory at site and building a living building having four stories or more.

This mutually joining structure of unit type construction for joining a lower side living unit D constituted using a steel pipe column in a column part and a shape steel member in a beam part and completing finish of the inside/outside parts and an upper side living unit U mutually is provided with lower column steel pipe columns 1a, 1b provided in the lower side living unit D, a lower column head outer side diaphragm 5 provided on the lower column steel pipe column, upper column steel pipe columns 2a, 2b provided in the upper side living unit U, an upper column leg outer side diaphragm 4 provided on the upper column steel pipe column, and a plurality of bolts 7 for joining columns longitudinally and joining the lower column head outer side diaphragm 5 and the upper column leg outer side diaphragm 4 mutually.