We report experimental results on relationship between polymer chain architecture and morphology of microdomains of asymmetric linear triblock copolymers, S1BS2 (S: polystyrene; B: polybutadiene). For this purpose, we synthesized various asymmetric triblock copolymers having different lengths of two end-blocks. The morphology was examined by small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). Although total molecular weight, composition, and thermal annealing temperature were kept constant, the morphology was found to change with a degree of chain asymmetry. One typical example exhibits a morphological change as cylinder lamella cylinder with a decrease in length of the shorter S-2 end-block chains, while keeping the total molecular weight and the total polystyrene composition constant. This curious morphological behavior exhibiting a re-entrant type change is qualitatively in accord with the self-consistent field theory (SCFT) results by Matsen [J. Chem. Phys. 2000, 113, 5539-5544]. This indicates that SCFT results about the morphological phase behavior of block copolymers are useful guides for experiments as long as the preparation of block copolymer samples is precisely controlled. The re-entrant behavior predicted by SCFT for the asymmetric triblock copolymers is attributed to the pull-out of the shorter end-block chains from their preferred microdomain. Namely, when pull-out of the shorter S-2 end-block chains from a S-microdomain takes place, the shorter S-2 end-block chain is solubilized in B-microdomains. As a result, the effective polybutadiene composition is increased. This kind of mechanism, the solubilization of the shorter A(2) end-block chains, may be relevant to the re-entrant type change of morphology with the degree of the chain asymmetry, and it has been experimentally confirmed by the lowering of T-g of the middle blocks and the lowering of the chain mobility of the shorter M-2 end-blocks by the electron spin resonance using spin-labeled M1SM2 (M: poly(methyl acrylate), and the shorter M-2 end-block chains were spin-labeled) specimens. It is confirmed by this study that the architecture asymmetry is an important factor in addition to the composition and the degree of the segregation, impacting the morphological phase behavior of block copolymers.