Japanese Crown Prince Naruhito said Thursday his wife, Masako, feels better about her health since making her first official overseas trip in more than a decade.

The 49-year-old crown princess developed a stress-induced illness soon after giving birth to the couple's only daughter, Aiko, now 11.

The couple visited the Netherlands on April 28-May 3 to attend King Willem-Alexander's inauguration, their first official overseas trip together since a 2002 visit to New Zealand and Australia.

Naruhito said Masako's symptoms have had ups and downs over the past decade, but that she seems more confident about her health since the trip and hopes to slowly expand her activity.

"We were very careful so she could stay in good health. I'm relieved that her effort came to a fruition," he told a news conference Thursday.

Naruhito said it was a difficult decision to make the overseas trip. They decided to go after consulting with palace doctors, hoping "it could be a good chance for her to take a new step forward," he said.

"I believe successfully completing the overseas trip gave Masako confidence," he said.

Naruhito said Masako will not join him on a visit to Spain next week because of the busy schedule — five cities in six days.

The trip begins a day after the couple's 20th wedding anniversary, which he did not mention during the news conference.

He said he will attend events marking the 400th anniversary of exchanges between Japan and Spain since a mission by a Japanese feudal lord in 1613.