© 2017, Electromagnetics Academy. All rights reserved. We measured millimeter-wave dielectric parameters of magnesium fluoride glass wafers at the room temperature in the frequency band of 75-110 GHz by applying the open resonator technique based on the use of Bragg structures and related multi-layer assemblies. Through the comparison of measured and simulated transmission spectra of various structures, the dielectric constant of magnesium fluoride glass is found as ε = 5.50±0.01. The estimate for the loss tangent is found to be tan δ = 0.00005, with a possibility that the actual losses could be smaller than this value.