Human shampoo should not be used on dogs. Most shampoos have ingredients in them that may cause skin irritation in animals. Using dog shampoo would be the best option to reduce chances of health problems in dogs.
1 Additional Answer
You can, but it won't be as beneficial for him/her as an animal shampoo would be. Unless the shampoo you use on your hair is really strong, chances are it won't get your dog as clean and fresh as you'd like. You can find more information here: http://www.manentail.com/home2.asp