To produce a builder having an excellent chelating capacity, biodegradability and economical profit, to produce it at good efficiency and to obtain a detergent composition containing builder and excellent detergency and friendly to the environment.

This builder comprises a polymer obtained by grafting an ethylenically monomer such as acrylic acid onto sorbitol. The production process comprises grafting an ethylenically unsaturated monomer onto sorbitol in the presence of a polymerization initiator under conditions including a temperature of -30 to 100°C and a pH of 5-9. The detergent composition comprises a surface active component and the above builder.