To simply and rapidly attach or detach a squeegee, to prevent the squeegee from being deformed due to a sliding resistance from a plate surface at the time of screen printing, to reduce a clamping force of the squeegee, and to reduce ducts generated from a clamp unit.

A squeegee fixing mechanism for a screen printer fixes a squeegee holder 33 from an inside of a scraper 37 side by a holder clamp 43. The mechanism operates the clamp 43 from an outside. The clamp 43 has a sectional inverted L-shaped clamp body 45, and a presser 47 provided at a rear part of the holder 33. The presser 47 is provided at a lower part 51a of the lower base from a pivotal support 49 of the base 51 pivotally secured to a clamp body, and operated by an operating mechanism 55 capable of operating the upper part 51b of the base above the support 49 of the base 51 from the outside. The mechanism 55 is formed of a screw mechanism 57, a cylinder mechanism 61, a cam mechanism 65, a spring mechanism 71 and the like.