Sb2Te3 is well known as a phase-change material, and is expected to exhibit high spin-charge current conversion because of its strong spin-orbit interactions. Reversible phase-change characteristics enable manipulation of physical properties depending on phase. Therefore, it is anticipated that its spin properties can also be tuned by controlling the phases of Sb2Te3, promising great potential for novel spintronic devices. However, the effects of crystallinity on the spin properties of Sb2Te3 have not yet been investigated. Herein, the spin relaxation induced by the spin-pumping effect in CoFeB/Sb2Te3 bilayers is examined using ferromagnetic resonance (FMR) at 300 K for crystalline and amorphous Sb2Te3. FMR signal width enhancement is observed for the highly oriented crystalline Sb2Te3 film at thickness less than 7 nm. In contrast, the FMR signal widths of the amorphous sample are independent of the layer thickness. The significant increase in linewidth suggests more efficient spin injection from the ferromagnetic CoFeB layer into crystalline Sb2Te3 than into amorphous Sb2Te3. This stark contrast between the spin dynamics of the amorphous and crystalline Sb2Te3 films supports the idea that spin conduction can be tuned by controlling the crystal orientation of Sb2Te3 films.