All you have to do is look at the dial and it will be written on there. Though it mainly only states the country when all the bits and pieces were screwed and glued together for the final assembly. Seiko has several movements that are made in one country then shipped to another country for installation in the case. Many new7S26 movements are unfortunately assembled in China and many Seiko 5 models are assembled in Singapore. The 7S26 is the most common movement for the Seiko five so that is the most likely unit you would be referring to if the watch is newer. Older 7S26 models use to be made in Japan.
Michael
Michael