There is provided an acid addition salt of (-)-(3R)-quinuclidin-3-yl(1R)-1-phenyl-1,2,3,4-tetrahydroisoquinoline-2-c- arboxylate with an acid selected from the group consisting of (-)-(2S,3S)-tartaric acid, (+)-(2S,3S)-di-O-benzoyltartaric acid, (+)-(2S,3S)-di-O-(4-methylbenzoyl)tartaric acid, (-)-L-phenylalanine, benzenesulfonic acid, cyclohexanesulfamic acid, hydrobromic acid, naphthalene-2-sulfonic acid, sebacic acid, (+)-camphor-10-sulfonic acid, p-toluenesulfonic acid, ethanesulfonic acid, methanesulfonic acid and methyl phosphate, which has little hygroscopicity that affects the use as a drug or its drug substance, and is very useful as a drug or its drug substance.