Problem to be Solved To provide a novel compound inhibiting the effect of HSP90, in particular a novel compound inhibiting the function of HSP90 as a chaperone protein and having antitumor activity. Solution The present invention provides a pyrazolopyrimidine compound represented by the formula (1) having various substituents which inhibits the ATPase activity of HSP90 and which has antitumor activity, an HSP90 inhibitor comprising the compound represented by the formula (1), a medicament comprising the compound represented by the formula (1), an anticancer agent comprising the compound represented by the formula (1), a pharmaceutical composition comprising the compound represented by the formula (1) and a method for treating cancer using the compound represented by the formula (1).
