To provide a flame-retardant resin composition which exhibits excellent flame retardancy without using a halogen compound nor a phosphorous compound.

The flame-retardant resin composition contains a resin A, a solid acid B, and an inorganic filler whose dehydration starts in a temperature range from -50C being the thermal decomposition temperature of a mixture of A and B to +50C. As the resin A, a compound containing an organic acid group and/or an organic acid ester group is preferable. As the solid acid B, a substance containing an oxide of silicon and nitrogen ion is preferable. As the inorganic filler C, a compound selected from the group comprising magnesium oxide, aluminum oxide, basic magnesium carbonate and hydrotalcite is preferable.