Magnetic topological materials have attracted much attention because of their exotic topological quantum physics arising from the interplay between spintronics, crystallography, magnetism, and topology. Based on first-principles calculations and crystal symmetry analysis, we present a lot of materials with fully spin-polarized nodal boxes in a ferromagnetic cubic structure. This nodal box is formed by six butterflylike nodal lines in the Brillouin zone when neglecting the weak spin-orbit coupling (SOC) mainly from F atoms. Such a fully spin-polarized nodal box is reported here. The ${M}_{110}$ mirror symmetry is not broken in [110] magnetization direction, thus leaving a symmetrically protected butterflylike nodal line on the (110) surface when the SOC is present. The band gaps of the nodal box induced by SOC are less than 1 meV due to the weak SOC effect. Our discovery fills the gap in the study of a fully spin-polarized nodal box in the magnetic system and provides a good research platform for studying the combination of new topological states and spintronics. Such a fully spin-polarized nodal box with unique Fermi surfaces and surface states traversing the Brillouin zone holds great promise for applications in catalysis and spin transport.