A glass bulb for a cathode ray tube comprising a panel portion having a substantially rectangular face portion and a funnel portion having a neck portion, wherein when the glass bulb is used for a cathode ray tube, the glass bulb at least regionally suffers from a tensile stress resulting from the atmospheric pressure on the outer surface of the glass bulb having a vacuum inside, at least part of the face portion of the panel portion where the tensile stress over the face portion has a maximum value .sigma..sub.VP has a compressive stress layer formed by chemical tempering on the outer surface, and the .sigma..sub.VP, the magnitude of the compressive stress on the compressive stress layer .sigma..sub.C MPa, and the thickness of the compressive stress layer t.sub.C .mu.m satisfy the following relationship: 120/t.sub.C.gtoreq.(1-.vertline..sigma..sub.VP /.sigma..sub.C.vertline.)>30/t.sub.C provided that .sigma..sub.VP.gtoreq.20 MPa.