A novel quinaldinamide derivative having the formula: ##STR1## wherein each of R.sup.1 and R.sup.2 independently represents a lower alkyl group or R.sup.1 and R.sup.2 are combined together with the adjacent nitrogen atom to form a 5-7 membered ring; and X represents the hydrogen atom, a lower alkyl group or a lower alkoxy group, and its acid-addition salt, which show prominent central muscle relaxant effect, namely rigidity relieving effect on anemic decerebrated rigidity.