To prevent substances falling from packaged objects such as so-called noodle dregs and various types of other foreign matters from being mixed in the side of a center sealing device by a simple configuration.

The horizontal pillow packaging machine includes: a bag making machine 20 for forming a continuously fed band-like film 1 into a cylindrical shape so that both side edges of the film 1 are overlapped with each other on the lower side; the center sealing device disposed downstream of the bag making machine 20; and an end sealing device, etc. At a portion immediately before a portion where both side edges of the band-like film 1 are overlapped with each other in the bag making machine 20, a biting prevention guide 50 for preventing intrusion of a small object between both side edges is arranged. The biting prevention guide 50 has a Y-shaped cross section. A V-shaped portion of the Y-shape serves as a body 50a, and an I-shaped portion 50b of the Y-shape is fixed while entering between a pair of vertical portions hung downwardly from bottom portions 41a, 42b of the bag making machine 20. Each of both side edges of the band-like film 1 is made to pass between the vertical portion and the I-shaped portion.