This image (or other media file) is in the public domain because its copyright has expired.
This applies to the United States, Canada, the European Union and those countries with a copyright term of life of the author plus 70 years.
Note that a few countries have copyright terms longer than 70 years: Mexico has 100 years, Colombia has 80 years, and Guatemala and Samoa have 75 years. This image may not be in the public domain in these countries, which moreover do not implement the rule of the shorter term. Côte d'Ivoire has a general copyright term of 99 years and Honduras has 75 years, but they do implement that rule of the shorter term.
This image is now in the public domain because its term of copyright has expired in China. According to copyright laws of the People's Republic of China (with legal jurisdiction in the mainland only, excluding Hong Kong and Macao) and the Republic of China (currently with jurisdiction in Taiwan, the Pescadores, Quemoy, Matsu, etc.), all photographs enter the public domain fifty years after they were first published, and all non-photographic works enter the public domain fifty years after the death of the creator.
To uploader: Please provide where the image was first published and who created it.