Ulloa, deputising for the suspended Jamie Vardy, scored twice, with Riyad Mahrez and Marc Albrighton also on target as Claudio Ranieri's side leapt eight points clear of second-place Tottenham Hotspur.
Vardy's 22 goals and partnership with Shinji Okazaki have obliged Ulloa to wait for his opportunities this season, but having netted a stoppage-time penalty in last weekend's 2-2 draw with West Ham United, the Argentine striker proved his worth anew against Swansea.
"I'm happy because this team is unbelievable," Ulloa told Sky Sports at Leicester's King Power Stadium.
"We played so well. We miss Jamie Vardy because he is a good player, but we can still play well and I enjoy playing with this team and with these team-mates.
"We played a really good game and it is a massive three points. It is good for me because I needed confidence and after the last goal I was more confident, but I am more pleased about the three points."