The present disclosure relates to a housing assembly applied to an off-axis (lay-shaft) type reducer. The housing assembly with an improved oil churning function to which a plurality of gears of a vehicle reducer are coupled comprises: a cover housing including one surface coupled to a differential gear and a first counter gear, a middle housing including one surface that is coupled to an input gear and a second counter gear coupled to the first counter gear, wherein the one surface is provided to face the one surface of the cover housing, and lower end communicates with a sump space and an oil guide part machined and disposed on the cover housing and the middle housing to guide a flow direction of churned oil.