There is provided a T-type calcium channel blocker that is optically active 1,4-dihydropyridine compound, a pharmaceutically acceptable salt thereof or a solvate thereof, of formula (1) ##STR00001## wherein R.sup.1 and R.sup.2 are independently of each other C.sub.1-6 alkyl group or R.sup.1 and R.sup.2 together form --CR.sup.5R.sup.6--CR.sup.7R.sup.8, --CR.sup.5R.sup.6--CR.sup.7R.sup.8--CR.sup.9R.sup.10-- or --CR.sup.5R.sup.6--CR.sup.7R.sup.8--CR.sup.9R.sup.10--CR.sup.11R.sup.12--- , etc., X.sup.1 and X.sup.2 are independently of each other O or NR.sup.13, Ar is optionally substituted phenyl group, etc., R.sup.a and R.sup.b are independently of each other C.sub.1-6alkyl group, --L.sup.2--NR.sup.16R.sup.17, CH.sub.2O--L.sup.2--NR.sup.16R.sup.17CN, --L.sup.2--N(CH.sub.2CH.sub.2).sub.2NR.sup.16 or NR.sup.16R.sup.17, etc., Y is C.sub.1-20 alkyl group, --L.sup.3--NR.sup.18R.sup.19 ##STR00002## and * is absolute configuration of R.