Flame-retardant resin composition

A flame-retardant resin composition, which comprises a base resin (A), an organic phosphorus compound (B), and a flame-retardant auxiliary (C), wherein the organic phosphorus compound (B) comprises at least one member selected from the group consisting of compounds represented by the following formulae (3-1), (4-1) and (4-2):

• wherein Ar represents an aromatic hydrocarbon ring or a nitrogen-containing aromatic heterocycle;
• X1 represents an oxygen atom or a sulfur atom;
• X2 represents an oxygen atom or a sulfur atom;
• Y3 represents a 5 to 10-membered ring which contains P and X2 as ring-constituting atoms and may have a substituent, Y4 and Y5 are the same or different from each other and each represents a 4 to 10-membered ring which contains P as a ring-constituting atom and may have a substituent;
• Z2 represents an alkylene group;
• R1 represents an organic group;
• R2 represents a hydrogen atom, an alkyl group, or a group represented by the following formulae (3a) or (4a):
• wherein X1, X2, Y3, Y4 and Y5 have the same meanings defined above;
• “b” denotes an integer of 1 to 6;
• “c” represents an integer of 0 to 9;
• and “e” represents 0 or 1.