PURPOSE: To keep the replacement workability of a cylindrical printing component such as a cylindrical blanket compatibly with the supporting accuracy of a printing cylinder such as a blanket cylinder by a simple structure.

CONSTITUTION: In a printing cylinder retaining device for a printer, in which shaft sections 51 provided on both ends of the printing cylinder are supported at the center rotatably on frames 35 by bearing components 55 mounted on the frames 35 disposed on both sides of the printing cylinder respectively and a cylindrical printing component is fitted removably on the outer peripheral face section of the printing cylinder in the axial direction, a fitting and removing opening section 59 of the cylindrical printing component is formed on one frame 35. Two bearing retaining components 65 and 67 of centripetal half-spread shape are disposed face to face on the fitting and removing opening section, and two bearing retaining components 65 and 67 are provided between a holding position for holding the bearing components 55 centripetally by clamping the bearing components 55 from both sides and an unholding position for forming an opening for separating the bearing components 55, releasing the retention of them and passing the cylindrical printing component through between them in the direction of bringing them into contact with each other and separating them away.