Vehicle body frame for motorcycle

A vehicle body frame (1) of a motorcycle comprises a front frame portion (3) extending rearward from a head pipe (2), and a rear frame portion (5) extending rearward from a rear end of the front frame portion (3). The front frame portion (3) includes a pair of right and left frame members (30,31). A forward portion of the rear frame portion (5) is a lumber frame (5) having a closed cross-section structure portion in which a pair of right and left steel plates (50,51) are joined together.