It is almost certain that this person is Matthew. In the parallel account of this narrative in the Gospel of Matthew, we see that Levi appears to be "renamed" Matthew.
Matthew 9:9 (NIV)
9As Jesus went on from there, he saw a man named Matthew sitting at the tax collector’s booth. “Follow me,” he told him, and Matthew got up and followed him.
It is unknown why Levi is called Matthew in this gospel. Like all the gospels, Matthew is actually an anonymous document, and our attribution of it to Matthew is based on the consensus of Church Fathers in the 2nd century. However, it appears that whoever wrote the gospel (hereafter called the evangelist) wants to show that Levi is the Matthew listed in the Twelve (cf Matthew 10:3).
This could be "...because the writer believed that Levi was or should have been one of the twelve, or is it perhaps because in writing of himself he preferred the name Matthew to his own pre-conversion name, Levi?" [Hagner, Introduction, lxxvi].
Though there are theories that claim the evangelist is playing with names, it must be said that it is very unlikely that he would get away with substituting the name Levi for Matthew if they were not the same person. It is not unusual for individuals in 1st century Israel to have more than one name. For example, it seems that another member of the twelve is known by two names: Jude, was also known by the name Thaddeus. (See Mark 3:16-19 vs Luke 6:14-16)
Suffice it to say, that the vast majority of scholars suggest that the "Levi" of Mark 2 and Luke 5 is indeed the Matthew of Matthew 9. Why the evangelist sought to enlighten his readers to this is speculative.
Hagner, D. A., Word Biblical Commentary - Matthew 1-13, Nelson, 1993.
Cole, A., Mark, IVP, 2008
Nolland, J., Word Biblical Commentary - Luke 1-9:20, Nelson, 1989