Magnetism in stacked triangulenes is investigated using the Hubbard-type model with onsite repulsions. We show that the open shell electronic structure can be an origin of the decreasing magnetic moment with adsorption of molecules. Next, possible ferromagnetic solutions are studied, as one of the candidates of molecular magnets. Ferromagnetism is stable in regions with large interlayer hoppings and large onsite repulsions, whose properties are discussed also.