The high-temperature dimensional stability of β-spodumene solid solution (s.s.) glass-ceramics with different crystallinities was investigated. It was demonstrated that the glass-ceramics show volume change due to structural relaxation in the residual glass phase regardless of crystallinity, even in the specimen with a high crystallinity of 90 vol%. The volume change process was expressed by the Kohlrausch-Williams-Watts (KWW) function. In the specimens with lower crystallinity (52, 71 vol%), normal relaxation behavior like that of non-crystalline glasses was observed, with activation energies of 599 and 414 kJ/mol, respectively. In contrast, the specimen with a crystallinity of 90 vol% showed an anomalous relaxation behavior accompanied with a densification limit and lower activation energy (250 kJ/mol). This anomalous behavior was attributed to the inner friction caused by proximity of the crystal grains in the glass-ceramic, which may result in a blocking effect on the volume shrinkage. We predicted the long-term dimensional stability of a precision glass-ceramic capillary for fiber-optic devices, based on the relaxation data in the KWW function.