The present invention provides a novel pyrazolopyrimidine compound of the formula [I]: wherein R′ is (A) a substituted aryl group, (B) an optionally substituted nitrogen-containing aliphatic heteromonocyclic group, (C) a substituted cyclo-lower alkyl group, (D) an optionally substituted amino group, or (E) a substituted heteroaryl group, R2 is (a) an optionally substituted heteroaryl group or (b) an optionally substituted aryl group, Y is a single bond, a lower alkylene group or a lower alkenylene group, Z is a group of the formula: —CO—, —CH2-, —SO2- or a group of the formula [II]: Q is a lower alkylene group, and q is an integer of 0 or 1 or a pharmaceutically acceptable sait thereof, which has a small conductance potassium channel (SK channel) blocking activity and is useful as a medicament and a process for preparing the same