A packaging machine, of the type comprising a bed mounted on support legs, two uprights rigidly connected to the bed and upwardly projecting therefrom, and a working head carried by said uprights. The bed (1) comprises a rectangular box-formed sheet metal frame and two central, longitudinal, side-by-side cross-members (1e, 1f); the constituent elements of at least part of the machine working units being mounted directly on said cross-members, and a space for housing removable roller tables being provided between these cross-members (1e, 1f) and the longitudinal sidepieces (1a, 1b) of the bed.