Abstract: An electromagnetic retarder apparatus with a built-in exciter having a retarder exciter inside thereof for generating braking torque by an eddy current produced in an eddy-current cylinder as a plurality of magnetic poles that are alternately magnetized to N and S poles by a field current caused to flow by a voltage generated in the exciter are caused to rotate in a relation to the eddy-current cylinder disposed at a location facing the magnetic poles; the eddy-current cylinder comprises a core formed by laminating a magnetic material, and short-circuiting method provided on the laminated core in the axial direction thereof for causing the generated eddy current to flow therein.