Kitayama turned professional in 2015. He played mostly on the
Web.com Tour in 2016 and 2017 with little success and was ranked 1174 in the world at the end of 2017. In 2018, Kitayama played mostly on the
Asian Tour. He played a single
Asian Development Tour event, the PGM Darulaman Championship in Malaysia, which he won. He had some good finishes on the Asian Tour, including tied for 4th in the
New Zealand Open, joint runner-up in the
Royal Cup and joint 4th in the
Asia-Pacific Diamond Cup Golf, an event co-sanctioned with the
Japan Golf Tour. In November 2018, he finished tied for 3rd place in the
European Tour Q-School to earn a place on the
2019 European Tour. In just the second event of the season, the
AfrAsia Bank Mauritius Open, played in late 2018, he won by two strokes. The event was co-sanctioned with the
Sunshine Tour and the
Asian Tour. The win lifted him into the top 200 of the world rankings. In March 2019, he became the fastest player to two wins in European Tour history when he won the
Oman Open in only his 11th career appearance. In September 2021, he earned his
PGA Tour card by finishing 23rd in the
Korn Ferry Tour Finals. In February 2022, he recorded a 3rd place finish at
The Honda Classic. In May 2022, Kitayama improved upon this performance, recording a T2 finish at the
Mexico Open. In March 2023, he earned his first PGA Tour victory by winning the
Arnold Palmer Invitational. In July 2025, he earned his second PGA Tour victory at the
3M Open. In the third round, he shot a career-best and tournament-record-tying 60 that put him within one of the leaders. The win moved him into the top 70 in the
FedEx Cup standings and secured a spot in the
FedEx Cup Playoffs. ==Amateur wins==