A photo printer including a printer body having a printing engine disposed therein, a conveying unit to reciprocate a printing medium supplied to the printing engine, a supplying unit disposed at an upper portion of the printer body to supply the printing medium to the printing engine, a supplying passage to guide the printing medium from the supplying unit to the printing engine, a retrograding passage disposed in the printer body to guide a preceding end of the printing medium inside and outside the printer body when the printing medium supplied to the printing engine is aligned and reciprocated, so that the printing medium is printed from a rear end thereof, and a discharging passage to discharge the printing medium outside the printer body when the printing of the printing medium is completed at the printing engine.