This study focuses on the reasons for re/by-election as a factor influencing voting participation and the results of the Korean National Assembly re/by-election after democratization. Existing research examines the re/by-election of a National Assembly as a kind of complementary and subordinate election to national elections, employing the midterm evaluation model, the election campaign model, or the turnout model. This paper argues that voters will participate in and vote in order to hold those responsible for re/by-elections accountable. According to the findings, voters are more likely to vote when incumbents commit illegal acts and are forced to resign by judicial decisions, as opposed to when incumbents resign for personal reasons. Furthermore, when an incumbent party re-appoints a candidate for a re/by-election despite previous incumbents of the party committing illegal acts and resigning by force, voters are more likely to reject that party’s candidate. This study shows, using a new variable of the reason for the re/by-election, that voters participate in and choose to vote in order to hold the political elite accountable for the re/by-election.