A dioxazine compound represented by the following formula in the free acid form, ##STR1## wherein V is a direct linkage or ##STR2## in which R.sub.3 is hydrogen or alkyl, X is a direct linkage or an aliphatic, araliphatic or aromatic bridging group, Y is phenylene or naphthylene, Z is a so-called vinylsulfone type fiber reactive group, and R.sub.1 and R.sub.2 are each hydrogen or alkyl, which is useful for dyeing or printing fiber materials to give a dyed or printed product of a blue color superior in fastness properties with superior build-up property.