The red phosphorus base flame retardant for an epoxy resin is provided,
which has red phosphorus particles coated with a thermosetting resin
containing an anhydrous zinc compound. The coated red phosphorus has
properties that a slurry having the coated red phosphorus dispersed in 10%
by weight into water at 20.degree. C. has an electric conductivity of 30
.mu.s/cm or below, the slurry having been left standing at 80.degree. C.
for 20 hours has an electric conductivity of 150 .mu.s/cm or below, and
when 80 ml of water is added to 8 g of the coated red phosphorus and
heated at 80.degree. C. for 20 hours, a concentration of PO.sub.4 ions
eluted is 10 ppm or below.
