64 bit Microsoft SQL Server Data Tools
As the others have said, there is only a 32 bit version.
The important thing is, if you’re running an x64-based SQL instance (64-bit), make sure to select “New Instance” on the Installation Type page, and NOT “Add features to an existing instance”. Not doing so will cause it to error out.
Only 32 bit version of SQL Server Data Tools published by Microsoft.
SQL Server comes in x32 and x64 but Visual Studio comes in only x32.
So if you have x64 SQL Server 2014, you can only install SQL Server Data Tools x32 in a new instance configuration. This will install Visual Studio 2013 x32.
However if you have SQL Server 2012, SQL Server Data Tools are available in the installation media (unlike SQL 2014 where it has to be manually downloaded & installed).