A printing device, for pressing a thermal head and a platen against each other, via an ink ribbon, to form an image on a film-shaped intermediate transfer medium, and for transferring the thus obtained image to a printing medium, comprising: a printing section (9, 12), including the thermal head and the platen, and being movable between a retracted position, whereat the thermal head and the platen are separated, and a printing position, whereat the thermal head and the platen are pressed against each other; an intermediate transfer medium conveyance section (5, 6, 13, M1, M2, M3), for conveying the intermediate transfer medium; an ink ribbon conveyance section (7, 8, M4, M5), for conveying the ink ribbon; a first mark detection section having a first mark detection sensor, for detecting a first mark formed on the intermediate transfer medium; and a control section, for controlling the printing section (9, 12), the intermediate transfer medium conveyance section (M1, M2, M3) and the ink ribbon conveyance section (M4, M5) based on information output by the first mark detection section, so that when the first mark detection section has detected the first mark, the printing section (9, 12) is positioned in the printing position, and thereafter, when the first mark has been detected by the first mark detection section during conveyance of the intermediate transfer medium and the ink ribbon, a printing process is begun, chararcterized in that the control section controls the printing section (9, 12), the intermediate transfer medium conveyance section (M1, M2, M3) and the ink ribbon conveyance section (M4, M5) such that, in a state that the first mark is present upstream of the first mark detection sensor in a conveyance direction employed for image forming and the first mark detection sensor has not yet detected the first mark, the printing section (9, 12) is moved to the printing position; and wherein, in a state that the thermal head and the platen are pressed against each other, the intermediate transfer medium is conveyed downstream in the conveyance direction for image forming to detect the first mark while conveying of the intermediate transfer medium and the ink ribbon is continued, and when the intermediate transfer medium and the ink ribbon reach a printing start position, image forming is started. a printing section (9, 12), including the thermal head and the platen, and being movable between a retracted position, whereat the thermal head and the platen are separated, and a printing position, whereat the thermal head and the platen are pressed against each other; an intermediate transfer medium conveyance section (5, 6, 13, M1, M2, M3), for conveying the intermediate transfer medium; an ink ribbon conveyance section (7, 8, M4, M5), for conveying the ink ribbon; a first mark detection section having a first mark detection sensor, for detecting a first mark formed on the intermediate transfer medium; and a control section, for controlling the printing section (9, 12), the intermediate transfer medium conveyance section (M1, M2, M3) and the ink ribbon conveyance section (M4, M5) based on information output by the first mark detection section, so that when the first mark detection section has detected the first mark, the printing section (9, 12) is positioned in the printing position, and thereafter, when the first mark has been detected by the first mark detection section during conveyance of the intermediate transfer medium and the ink ribbon, a printing process is begun, chararcterized in that the control section controls the printing section (9, 12), the intermediate transfer medium conveyance section (M1, M2, M3) and the ink ribbon conveyance section (M4, M5) such that, in a state that the first mark is present upstream of the first mark detection sensor in a conveyance direction employed for image forming and the first mark detection sensor has not yet detected the first mark, the printing section (9, 12) is moved to the printing position; and wherein, in a state that the thermal head and the platen are pressed against each other, the intermediate transfer medium is conveyed downstream in the conveyance direction for image forming to detect the first mark while conveying of the intermediate transfer medium and the ink ribbon is continued, and when the intermediate transfer medium and the ink ribbon reach a printing start position, image forming is started.