According to this survey in 2015 (http://www.igmchicago.org/surveys/15-minimum-wage), economists do not have a clear opinion on a 15 dollar minimum wage. "Uncertain" is the most common answer on whether it would cause unemployment, and "Agree" and "Disagree" both get considerable support.
Supposed by who, though? As you can see from the survey there was nothing like consensus on the question. The link in that article is to the National Restaurant Association, who are a lobbying organization.
