In a fulcrum bearing device for a pulley arm, a sleeve is inserted in a shaft hole formed in a boss portion of a pulley arm, washers are fitted on the outer peripheries of small diameter tube portions formed at the respective end portions of the sleeve, and the sleeve is fixed to an engine block by means of a bolt inserted through the sleeve and tightened, so that the pulley arm is pivotally supported. The shaft hole is formed at its respective end portions with seal receiving recesses having large diameters. Each seal member includes a cylindrical portion provided on its outer peripheral portion and press-fitted in the seal receiving recess, and a radial lip extending obliquely inwardly and provided on the inner periphery of the seal member. The distal end portions of the radial lips are kept in elastic contact with the outer diameter surface of the sleeve.