A perfector including: a printing unit configured to perform printing simultaneously on both surfaces of a sheet; detecting means (25, 27) for detecting printing conditions on both surfaces of the sheet on which the printing is performed simultaneously; and transporting means (13, 17) for holding and transporting the detected sheet to a discharging unit, wherein the printing unit includes: a first printing cylinder configured to hold and transport the sheet; and a second printing cylinder disposed lateral to the first printing cylinder and being in contact with the first printing cylinder, wherein the transporting means (13, 17) includes: a transfer cylinder being in contact with the first printing cylinder and configured to receive, from the first printing cylinder, the sheet on which printing is performed on both surfaces by the first printing cylinder and the second printing cylinder; and a delivery cylinder being in contact with the transfer cylinder and configured to receive the sheet from the transfer cylinder, and wherein the detecting means (25, 27) includes: a first checking camera configured to detect the printing condition on one surface of the sheet transported by the transfer cylinder; and a second checking camera configured to detect the printing condition on the other surface of the sheet transported by the delivery cylinder, wherein the first checking camera is disposed on the discharging unit side of the transfer cylinder, characterized in that the first checking camera is disposed to be capable of checking the sheet at a position on the circumferential surface of the transfer cylinder away from a contact position between the first printing cylinder and the transfer cylinder by a distance equal to or more than the length of the maximum-size sheet printable by the perfector from a leading end to a trailing end thereof. a printing unit configured to perform printing simultaneously on both surfaces of a sheet; detecting means (25, 27) for detecting printing conditions on both surfaces of the sheet on which the printing is performed simultaneously; and transporting means (13, 17) for holding and transporting the detected sheet to a discharging unit, wherein the printing unit includes: a first printing cylinder configured to hold and transport the sheet; and a second printing cylinder disposed lateral to the first printing cylinder and being in contact with the first printing cylinder, a first printing cylinder configured to hold and transport the sheet; and a second printing cylinder disposed lateral to the first printing cylinder and being in contact with the first printing cylinder, wherein the transporting means (13, 17) includes: a transfer cylinder being in contact with the first printing cylinder and configured to receive, from the first printing cylinder, the sheet on which printing is performed on both surfaces by the first printing cylinder and the second printing cylinder; and a delivery cylinder being in contact with the transfer cylinder and configured to receive the sheet from the transfer cylinder, and a transfer cylinder being in contact with the first printing cylinder and configured to receive, from the first printing cylinder, the sheet on which printing is performed on both surfaces by the first printing cylinder and the second printing cylinder; and a delivery cylinder being in contact with the transfer cylinder and configured to receive the sheet from the transfer cylinder, and wherein the detecting means (25, 27) includes: a first checking camera configured to detect the printing condition on one surface of the sheet transported by the transfer cylinder; and a second checking camera configured to detect the printing condition on the other surface of the sheet transported by the delivery cylinder, a first checking camera configured to detect the printing condition on one surface of the sheet transported by the transfer cylinder; and a second checking camera configured to detect the printing condition on the other surface of the sheet transported by the delivery cylinder, wherein the first checking camera is disposed on the discharging unit side of the transfer cylinder, characterized in that the first checking camera is disposed to be capable of checking the sheet at a position on the circumferential surface of the transfer cylinder away from a contact position between the first printing cylinder and the transfer cylinder by a distance equal to or more than the length of the maximum-size sheet printable by the perfector from a leading end to a trailing end thereof.