A vehicle door lock device includes: a housing having an opening; a coupling member configured to be coupled to an operation mechanism arranged on a door; an operation lever arranged inside the housing and coupled to the coupling member through the opening; and a cover capable of opening and closing the opening and a coupling point between the coupling member and the operation lever. The cover is separate from the housing and assembled to the housing to be mountable on and demountable from the housing and rotatable between opened and closed states. Each of the housing and the cover includes: a temporary retaining mechanism to temporarily retain the cover in the opened state when the cover is assembled to the housing in a rotatable manner; and a full retaining mechanism configured to retain the cover in the closed state when the cover is rotatably assembled to the housing.