Yes, HTTPS is a positive ranking signal, according to Google. Having a secure HTTPS website might provide a small advantage, as stated by Google:

“We’re starting to use HTTPS as a ranking signal. For now it’s only a very lightweight signal — affecting fewer than 1% of global queries, and carrying less weight than other signals such as high-quality content — while we give webmasters time to switch to HTTPS. But over time, we may decide to strengthen it, because we’d like to encourage all website owners to switch from HTTP to HTTPS to keep everyone safe on the web” – source

While HTTPs is a ranking factor, don’t expect significant ranking improvements just from moving from HTTP to HTTPs – source

HTTPS is used more like a deal breaker (“All other signals being more or less equal, it gives a page the edge needed to top the other result”), according to Gary Illyes: source

@MattSouthern more like a dealbreaker. All other signals being more or less equal, it gives a page the edge needed to top the other result

— Gary "鯨理／경리" Illyes (@methode) July 21, 2015