In one sense, you might say that it is true: Faustus is a Medieval Man presented as living in the Renaissance. The Faustus legend was based on a real historical figure. While there are more than one candidates for the original Faust, the most popular one, the one whose life is most easily traced, is German Doctor of Divinity Johann Faust, born around 1480, who took a doctoral degree from University of Cracow. A theologian, like Marlowe's Faustus, he practiced astronomy, alchemy and black magic. While his birth date places him at the end of the Medieval period, which is generally recognized as running from the end of the 400s through to the end of the 1400s, his life was mostly lived during the budding of the Renaissance. Thus he would have been jointly under the influence of fading Medieval ideas and growing Renaissance ideas. The first mention of Doctor Faust was in 1539 by Philip Begardi, and the first time the legend appeared in print was in a "chapbook" (signifying a species of inexpensive printing for tales and poems) sold at fairs and printed in 1587. Marlowe's play followed almost immediately in 1588 after translation to English.
In another sense, however, it is not correct to say Marlowe's Faustus was a Medieval man; this accords with the influence the original Faust would have felt from the newly influential Renaissance. Marlowe's text strongly indicates Renaissance characteristics for his Faustus. Faustus is shown to be a Renaissance Man and a Renaissance Individualist. He is a Renaissance Man because he knows several languages and has mastered every possible field of academic inquiry ranging from mathematics to law and economics. He is an Individualist because he no longer focuses on religious concerns ("Divinity, adieu!") that put spirituality in the forefront of motivation and ambition. Instead he concerns himself with material attainments, like wealth, power, control and magic. In summary, while Marlowe's Faustus starts out in a university that was founded and structured long ago according to Medieval principles, "I have been a student here these thirty years," he revolts against the Medieval norms, "These metaphysics of magicians, / And necromantic books are heavenly," and pursues his Individualistic ambitions with his eyes turned away from religious Heavenly reward and toward present-world material gain only, even if he has to sell his to gain it.
So Faustus ... [holds;]
There is no chief but only Belzebub;
To whom Faustus doth dedicate himself