Provided is a glass ceramic composition which can be fired at a temperature of 1000° C. or lower, and a sintered body of which has a low relative permittivity and a high Q value, stable temperature characteristic and high reliability, and is excellent in plating solution resistance. The glass ceramic composition provides a low dielectric constant layer for inclusion in a laminate glass ceramic substrate in a ceramic multilayer module. It includes a first ceramic having forsterite as the main constituent, a second ceramic having at least one of SrTiO3 and TiO2 as the main constituent, a third ceramic having BaZrO3 as the main constituent, a fourth ceramic having at least one of ZrO2 and MnO as the main constituent, and 3 weight % or more of a borosilicate glass containing Li2O, MgO, B2O3, SiO2 and ZnO, which further contains an additive constituent including at least one of CaO and SrO.