Yes, the devil is real. He is not just a symbol for evil, nor is he an imaginary figure that people dreamed up to explain the existence of evil. Evil is real and so is Satan or the devil.
Don't picture Satan, however, the way the cartoons do as a comic figure with a red suit and a pitchfork who bothers people sometimes but otherwise has little influence. Satan is a very powerful cosmic spiritual personality who has one goal: to stop God's work wherever it is taking place. To accomplish this he schemes and works every way he can, and he is behind all the evil that takes place in the world. His name Satan literally means "Adversary" and that is what he is: our adversary.
More than that, the devil works to deceive us and convince us that his promises are true and God's Word is a lie. Jesus said that the devil "was a murderer from the beginning, not holding to the truth, for there is no truth in him. When he lies, he speaks his native language, for he is a liar and the father of lies" (John 8:44). Don't ever take Satan lightly!
But one other thing needs to be said about the devil: He is a defeated foe! By His death and resurrection Jesus Christ conquered all the forces of death and Hell and Satan, and when we belong to Christ, we are safe from all these terrors forever. Make sure of your salvation by giving your life to Christ today.