A seat frame for a motorcycle includes a plurality of aluminum parts manufactured with different manufacturing methods. A seat frame includes front members, middle members, and a rear member, the front members, the middle members, and the rear member being formed of aluminum. The rear member is formed by integral molding based on a gravity casting method. The rear member includes a pair of left and right rail portions, a front cross portion, a rear cross portion, and a plurality of attachment bosses for attaching other parts. The left and right rail portions each have an attachment portion to be connected to a rear end portion of corresponding one of the middle members provided on an end portion thereof on the front side in the vehicle longitudinal direction.