Fiji won plaudits for their run at the tournament, which was ended by England in a 30-24 defeat in Marseille on Sunday, after which a visibly emotional Raiwalui praised his team and said they had laid a platform for the next generation of players.
"I guess it is time to make it official, specifically what the next cycle will look like for Fiji Rugby. I will not be seeking an extension of (my) employment with FRU past 31 December," Raiwalui confirmed on the social media platform X, formerly known as Twitter.
"Thanks again to the players, staff and all the supporters, it has been quite a ride!"
Fiji Rugby did not immediately respond to a request for comment by Reuters.
New Zealand-born Raiwalui was appointed coach in February this year after Vern Cotter stepped down, having previously been high performance director.
Fiji beat Australia and Georgia in Pool C but lost to Wales and Portugal. They rallied from 14 points down to draw level at 24-24 against England going into the final 10 minutes of their quarter-final, but lacked the experience to claim the win.
It was Fiji's first World Cup quarter-final since 2007 and their third overall.