To provide a hydrochloride of a tricyclic pyrazolopyrimidine compound inhibiting the effect of HSP90 and a crystal thereof. The present invention provides a hydrochloride of 2-{4-amino-2-[(3-chloro-4-methoxy-5-methylpyridin-2-yl)methyl]-2,7-dihydro-6-thia-1,2,3,5-tetraazabenzo[cd]azulen-8-yl}-N-methylacetamide which inhibits the ATPase activity of HSP90 and which has antitumor activity, a crystal thereof, a medicament comprising the same, an anticancer agent comprising the same, and the like.
