Provided are a blade device equipped with a blade member which can accurately adjust pressing force due to a blade member, and a printing machine and a coating device equipped with the blade device. A blade device according to the present invention has: a blade member contacting with a plate roll to which coating material is to be applied; an upper holder contacting with the blade member from one surface side of the blade member; a lower holder contacting with the blade member from another surface side of the blade member; a tube contacting with the blade member and configured to expand and contract by pressure of fluid; and a tube positioning part which is provided on the upper holder and positions the tube closer to the roller, in a direction in which the blade member extends, than a tip end of the lower holder is. The tube adjusts a pressing force, of the tip end of the blade member, against the roller by being expanded or contracted while being held by the tube positioning part and the blade member.