The present invention relates to a process for the production of a biguanide derivative useful as an intermediate for triazine-type herbicides, in which the biguanide derivative can be produced at high yields by reacting a phenoxyalkylamine salt with dicyandiamide in a solvent containing a paraffinic hydrocarbon having 8 to 15 carbon atoms, or by reacting a free phenoxylakylamine with a hydrogen halide in a solvent containing a paraffinic hydrocarbon having 8 to 15 carbon atoms and reacting the resultant a phenoxyalkylamine salt with dicyandiamide in the same solvent without isolating the phenoxyalkylamine salt.