A glass ceramics having a chemical composition of aRO.bNb.sub.2.O.sub.5.cSiO.sub.2.dB.sub.2O.sub.3.eTeO.sub.2.fX (where R represents Ba and/or Sr, X represents one or more oxide selected from the group consisting of TiO.sub.2, ZrO.sub.2, P.sub.2O.sub.5 and ZnO, a>b.gtoreq.0.05, 0.60.gtoreq.c.gtoreq.0, 0.70.gtoreq.d.gtoreq.0, 0.70.gtoreq.e.gtoreq.0, c+d+e.gtoreq.0.175, a+b+c+d+e=1.0 and 0.10.gtoreq.f.gtoreq.0). The ratio dielectric constant at 1 kHz .epsilon..sub.1 to dielectric constant at 100 kHz .epsilon..sub.100 (.epsilon..sub.1/.epsilon..sub.100) is 10 or more.
