We report experimental results of pressure-induced ordering of spheres on body-centered cubic (bcc) superlattice in a microphase-separated polystyrene-block-poly(ethylene-co-but-1-ene)-block-polystyrene (SEBS) triblock copolymer. After well-ordered bcc superlattice was prepared by annealing as-cast samples at 140 degreesC for 10 h, the samples were further pressurized at 50.7, 101.3, 202.7 and 405.3 Mpa at room temperature for 24 h. Small-angle X-ray scattering (SAXS) measurements revealed further ordering of the bcc spheres for the samples pressurized at 202.7 and 405.3 MPa, while the bcc regularity became worse for the samples pressurized at 50.7 and 101.3 Mpa. On the other hand, starting with an ill-ordered sample, no change in the SAXS profile was detected upon pressurizing at 405.3 Mpa up to 27.5 h. Thus, it turned out that the effect of pressure on the ordering of spherical microdomains is not straightforward.