No one knows the exact meaning of Jesus' title Son of Man. Apparently people who lived at the time of Jesus didn't understand it either, because hardly anyone called him by that title. Ironically in the Gospels it is the title Jesus used most often when referring to himself. He said it instead of “me” or “I.” Son of Man is used 30 times in the Gospel of Matthew. Before St. Stephen (the first martyr) was stoned to death, he said, “I see the heavens opened and the Son of Man standing at the right hand of God” (Acts 7:56).
By using Son of Man for himself Jesus could simply have been stressing the fact that he is truly human. This seems to be the way the expression is used in chapters 2-5 of the Book of Ezekiel in which the prophet is formally addressed as “son of man” over and over. Like the rest of us, Jesus is a son of Adam, and therefore he is our brother. He received his human body from Mary. As a man, Jesus knows what it means to be happy, pleased, and surprised as well as lonely, frustrated, tempted, and in pain. He can sympathize with us. As St. Hugh pointed out, the best doctor is one who has been sick. The title Son of Man carries overtones of suffering, and Jesus used it regularly when he spoke of his suffering and death.
The Son of Man can also be a term of glory. In the Book of Daniel it stands for a mysterious figure who represents all God's holy ones in a vision the prophet had.
Daniel saw in his vision:
One like a son of man coming,
on the clouds of heaven;
When he reached the Ancient One [God]
and was presented before him,
He received dominion, glory, and kingship;
nations and people of every language serve him.
His dominion is an everlasting dominion
that shall not be taken away,
his kingship shall not be destroyed.
By calling himself the Son of Man, Jesus could have been referring to this vision of the kingdom of God. It is Jesus after all who won salvation for us and is Lord of all.
In the Book of Revelation the author describes his vision of Christ in glory. He calls him “one like a son of man” (Revelation 1:13). Jesus especially used Son of Man when he was talking about the end of the world.
In summary, Son of Man can refer to Jesus' humanity or his divinity. In a way it is like him, in whom the human and the divine are one.
† SON OF MAN AND SON OF GOD, I ADORE YOU! †