PURPOSE: To provide a constant running control device for a vehicle which does not reduce the actual car speed to a set car speed remarkably, reduces an unpleasant feeling to passengers owing to the variation of the car speed, and can improve the fuel consumption property.

CONSTITUTION: When the opening signal of the throttle opening in a constant running control is continued for a specific time, in a constant running control device for a vehicle which maintains the car speed to a preset object car speed by controlling the throttle opening, the lockup of an automatic transmission is released. As a result, the lockup can be released at a desired time, a frequent shift down is not carried out, and an unpleasant feeling owing to the variation of the car speed to passengers can be reduced, and at the same time, the fuel consumption property can be improved. Furthermore, when the opening signal of the throttle opening is continued for a specific time, the lockup releasing (OFF) line IVB in the shift map of the automatic transmission may be moved in the direction to release the lockup easily (to the line IV C side).