PURPOSE: To provide a dwelling house unit in which a door is previously fitted to a vestibule entrance or a service entrance without spoiling transportability, and hence a load applied to the vestibule entrance or the service entrance at suspending the unit is reduced, and a construction method by the use of such process.

CONSTITUTION: In a dwelling house unit 1 used for a dwelling house having an unfloored part for a vestibule or a kitchen, it is provided with a vestibule entrance 2 or a service entrance continued from the unfloored part. A door part 6 is temporarily fixed to the vestibule entrance or the service entrance under the condition in which the lower end edge of the door part is conformed to the lower end edge of the dwelling house unit 1. Further the door part 6 is fitted to the vestibule entrance 2 or the service entrance slidably downward.