Ultraman hardly speaks lines unlike Ultra Seven though he lets out unique shouts performed by Masao Nakasone.
The god-like hero was portrayed thoroughly mysterious and dare not speak much.
Ultraman speaks lines only in Episode 1, 15, 33 and 39.
In speaking lines, the voice was acted as below:
Episode 1: Hisashi Kondo (film editor) Speaking to Hayata.
Episode 15: Koji Ishizaka (narrator) Speaking to kids to encourage them.
Episode 33: Hikaru Urano (narrator) Speaking to Alien Mefilas.
Episode 39 (the last episode): Hisashi Kondo (film editor) Speaking to Zoffy.
As Ultraman is set to speak by telepathy, the Earthlings couldn’t hear Ultraman talk to Mefilas in Episode 33.
It’s likely Mr. Nakasone was unable to voice Ultraman speaking lines because of the schedule.
It also seems to be explained recently Mr. Nakasone spoke lines for Episode 33 instead of Mr. Urano.
Incidentally, Zoffy was voiced by Mr. Urano.
In the case of Ultra Seven, the voice was always acted by Koji Moritsugu who played Dan Moroboshi including lines and the shouts which sound like “Djuwa!”
It’s said a voice actor was supposed to voice Seven but the shouting didn’t go well.
When Mr. Moritsugu gave it a try, he did a good job.
And it was decided he would voice Seven subsequently.
As Dan is Seven in his own, Mr. Moritsugu should be the right person.