travel diary; travel journal
A diary or journal kept while traveling, recording experiences, observations, and reflections.
彼は旅日記をつけながら日本中を歩いた。
He walked all over Japan while keeping a travel diary.
祖母の若い頃の旅日記を見つけた。
I found my grandmother's travel diary from when she was young.
旅行記 is a travelogue or travel account, often more formal or published, whereas 旅日記 is a personal diary.
Formed from 旅 “journey” and 日記 “diary”; 日記 retains its ordinary reading にっき.