Confined crystallization of the poly(ethylene glycol) (PEG) in poly(L-lactic acid) (PLLA) spherulite in a PLLA/PEG (50/50) blend specimen was studied by simultaneous small- and wide-angle X-ray scattering (SAXS/WAXS) measurements, where the blend specimen was subjected to the isothermal crystallization at 45.0 °C for PEG crystallization in the presence of preformed PLLA crystalline lamellae formed during the previous isothermal crystallization at 127.0 °C for 5–20 min. The WAXS results showed much suppression of the $\left(12\overline{4}\right)/\left(\overline{1}24\right)$ crystalline reflection peak for the blend as compared to the neat PEG, as well as much wider peak width for the same reflection. These results clearly indicate the suppression of the growth of the PEG lamellae in the thickness direction due to the space confinement by the preformed PLLA lamellae. The SAXS results also confirm the confined crystallization of PEG in the amorphous layer sandwiched by the preformed PLLA crystalline lamellae. Nevertheless, more regular stacking was formed due to the PEG crystallization as the neat PEG has the ability of forming very regular stacking of the crystalline lamellae, as evidenced by observing second-order peak in the SAXS profile for the blend specimen.