It seems a conflict to think that there is evidence of ghosts in the Bible, but there are many passages at least relating the belief in them at the time:
Matthew 14: 25-27
During the fourth watch of the night Jesus went out to them, walking on the lake. When the disciples saw him walking on the lake, they were terrified. "It's a ghost," they said, and cried out in fear. But Jesus immediately said to them, "Take courage! It is I. Don't be afraid."
Luke 24: 36-43
While they were still talking about this, Jesus himself stood among them and said to them, "Peace be with you." They were startled and frightened, thinking they had seen a ghost. He said to them, "Why are you troubled, and why do doubts rise in your minds? Look at my hands and my feet. It is I myself! Touch me and see; a ghost does not have flesh and bones, as you see I have." When he had said this, he showed them his hands and feet. And while they still did not believe it because of joy and amazement, he asked them, "Do you have anything here to eat?" They gave him a piece of broiled fish, and he took it and ate it in their presence.
1 John 4
Dear friends, do not believe every spirit, but test the spirits to see whether they are from God, because many false prophets have gone out into the world.
Proverbs 2:18
For her house leads down to death and her paths to the spirits of the dead.
Luke 16:23-31
A man calling out from hell. He answered, “then I beg you, send Lazarus to my father's house, for I have five brothers. Let him warn them, so that they will not also come to this place of torment.” Abraham replied, “They have Moses and the Prophets; let them listen to them.” “No, father Abraham,” he said, “but if someone from the dead goes to them, they will repent.” Abraham said to him, “If they do not listen to Moses and the Prophets, they will not be convinced even if someone rises from the sleep of the dead.”
Isaiah 14:9
The grave below stirs up to meet you at your coming; it rouses the spirits of the departed to greet you, all those who were leaders in the world; it makes them rise from their thrones, all those who were kings over the nations.
Luke 24:39
Behold my hands and my feet, that it is I myself: handle me, and see; for a spirit hath not flesh and bones, as ye see me have.