To provide a light crank case mounted in a crank part of a compact engine for a mower, a weeding and brushing machine, a chain saw and the like having excellent dimensional stability.

This invention relates to the crank case manufactured using a glass fiber reinforced polyamide resin component in which glass fibers (C) of 80 to 20 wt.% are blended for a polyamide resin component of 20 to 80 wt.% composed of polyamide resin (a) prepared by the polycondensation reaction of xylene diamine having metaxylene diamine as a main component and α,ω-straight chain aliphatic dicarboxylic acid of 100 pts.wt. and polyamide 66 (b) of 0.03 to 50 pts.wt. as a raw material.