Translation:He went to sleep late last night.
"He slept late last night" literally makes no sense in English. When you "sleep late" it means you get up later than usual. In English we would say he "went to sleep late" or more commonly, "went to bed late", because usually we are talking not about the hour someone actually fell asleep, but about the hour he went to bed.
This should really be "went to bed" rather than "went to sleep". Because we're not normally aware of when somebody or even ourselves actually fall asleep, which could be anywhere from the moment we get in bed to a couple of hours later.
"Went to sleep" is used for babies however.
Going to bed and going to sleep are distinct in English but I understand 睡觉 covers both.