The figure was revealed by chief financial officer Hiroki Totoki during Sony’s fiscal year 2018 results briefing.
Sony acquired cloud gaming company Gaikai in 2012, before using its technology and intellectual property to launch PlayStation Now in 2014.
Priced at $19.99/£12.99 per month or $99.99/£84.99 per year, the service is currently available in 19 countries.
“The average annual increase in paid subscribers has exceeded 40% since the service was launched and the number of users has increased around the same amount every year, reaching approximately 700,000 today,” said Totoki.
While the exact number varies by region, PlayStation Now plays home to over 750 PS3 and PS4 games, which Totoki said “is more than three times as many as the second largest game subscription service provider by number of titles”.
Since September 2018, PS Now users have also been able to download PS4 games in order to play them offline “without worrying about their network connection”, he added.
“Since the launch of this download service, gameplay time per user has grown significantly to the point where gameplay time on downloaded PS4 titles is double that of streamed titles, a trend which has contributed to higher user engagement with, and retention on, the PS Now service.”
Revealing the first PS5 details earlier this month, lead system architect Mark Cerny called Sony cloud-gaming “pioneers”, adding its vision in this area “should become clear” as the company heads toward the next-gen console’s release.
Microsoft is also expected to show off its upcoming cloud gaming service Project xCloud at E3 in June, ahead of the rollout of public trials later this year.