A blow molding apparatus (10) which can be simplified in structure, reduced in size and facilitated in maintenance, and which can improve the heat efficiency and equalize the temperature gradations. The blow molding apparatus (10) has a preform supply section (12), preform heating sections (14), a blow molding section (16), a product removing section (18) and a conveying section (20). The conveying section (20) intermittently conveys preforms (22) while maintaining a fixed spacing between adjacent preforms (22). The preform heating section (14) is divided into first and second heating portions (52,54). The first heating portion (52) has heaters (56) extending along the preforms (22) while the second heating portion (54) includes heaters (62a-62d) extending in the direction of preform conveyance and aligned vertically. The first heating portion (52) heats the preforms (22), and the second heating portion (54) applies a temperature distribution to the preform (22). The second heating portion (54) includes heaters (62a-62d) extending along the preforms (22) and disposed at positions where the preforms (22) stop intermittently on each side of the preform conveying path (20).