PURPOSE: To prevent release of slip limitation from delaying on account of excessive capacity and fuel cut from falling short on account of insufficient capacity by controlling lockup capacity at the time of coast running. CONSTITUTION: When a drive slip controlling state changes into a coast running state, ON or OFF of an air conditioner switch is judged at S66, S67. In case of ON, lockup pressure Pup is used for coast slip control high pressure at the time of operation of the air conditioner at S68. In case of OFF, the lockup pressure Pup is used for coast slip control low pressure at the time of non- operation of the air conditioner at S69, so that these pressures are applied to the coast slip control at S70. Since the lockup pressure Pup in a high load state of the air conditioner is made higher than that in low load state thereof, the lockup capacity during the coast running is made adequate according to load of the air conditioner, making it possible to prevent release of slip limitation from delaying on account of excessive capacity and fuel cut from falling short on account of insufficient capacity.