With formal experimentation receiving more attention as a means of enhancing reliability of syntactic argumentation within the field of experimental syntax, a few studies have begun to employ such a formal method in order to rigorously test the acceptability of double (or multiple) case-marking constructions. The present study shares this similarity with those previous studies; it also probes into double case-marking constructions in Korean via a formal experimentation (i.e., an acceptability judgment testing). Yet, this study is distinct from such studies to the extent that it substantially increases the empirical basis of the research on this topic on the following grounds. First, it used a sufficiently large sample size (193 participants). Second, it utilized a simple but efficient experimental task, viz. the binary Yes/No task. This task is ideal in that it best fits the assumption that human language works in a dichotomous way. Third, assuming that the double case-marking constructions are heterogeneous in nature, consisting of different sub-constructions whose syntactic operations are different, the present study investigated how different such sub-constructions are in acceptability judgments. Fourth, it compared acceptability judgments of the double case-marking constructions with those of the alternative forms with different markers or constructions being used. Such a comparison was made in a two-pronged direction, viz. within-type and between-type comparisons. More specifically, it was made in terms of the response time for each stimulus sentence as well as the proportion of the response (either `0` representing `unacceptable` or `1` representing `acceptable`). (Incheon National University, Korea University, Sangmyung University)