More particularly, the intended compound (I) of the present invention can be obtained by reacting a halide of guanidinobenzoic acid (II), i.e. a compound of the following formula (II'), obtained easily by, for example, heating the compound (II) together with thionyl chloride: ##STR9## wherein Hal represents a halogen atom such as chlorine or bromine, with the compound (III) in the presence of an a