Microscopic understanding of magnetization switching via domain nucleation and/or domain-wall propagation is fundamental knowledge for developing magnetic and spintronic devices. Here, we explore the underlying mechanism of the large coercivity of the magnetic Weyl semimetal Co3Sn2S2 thin films, which is roughly ten times larger than that of Co3Sn2S2 bulk single crystal, by measuring Hall resistance in constricted wire devices. The discretized steplike variations appear in the hysteresis loops of the Hall resistance in 0.6μm wide and narrower devices, indicating that the size of the reversed magnetic domain is comparable to the active area of the Hall devices. By counting the number of discrete features, the average diameter of the reversed magnetic domain is estimated to be 80 nm. Individually, the diameter of the reversed domain nucleus is evaluated to be roughly 2 nm. Considering the difference in the diameters of the reversed magnetic domain and the reversed domain nucleus, we ascribed the large coercivity of the Co3Sn2S2 thin films to a large nucleation field owing to the uniform crystallinity within grains and strong domain-wall pinning at grain boundaries specific to the thin films. With the large nucleation field in the films, an engineering of the domain-wall pinning sites is a promising approach to control the nucleation, manipulation, and detection of the single domain wall in Co3Sn2S2 thin-film devices.