To provide a compound which has a higher vulcanization efficiency and superior heat aging resistance compared to conventional compounding agents for rubber compositions and which is environmentally friendly.An amine salt compound of a carboxylic acid containing a thermal dissociation portion having the Formula (I): wherein R represents an organic group selected from a C1 to C20 alkyl group, a C3 to C10 cycloalkyl group, a C6 to C20 aryl group and a C7 to C30 alkaryl group, R1, R2 and R3 independently represent a hydrogen atom or a C1 to C20 organic group which may have a heteroatom and/or a substituent group and X represents a C2 to C20 organic group which may have a heteroatom and/or a substituent group and a compounding agent for rubber vulcanization and a rubber composition containing the same.