A device for manufacturing a fence post of mouldable material and provided with a reinforcement (12), which device comprises at least a multipart mould (1) with infeed (5) and air release opening (6), wherein the mould (1) is embodied with a lost part (11) on a longitudinal partition plane thereof, which lost part (11) forms a part of the end product, whereby as fence post this product can easily be provided with fixing members, for instance for fence wire mesh, and which end product is light in weight and easy to place in the ground.