A load measuring device for a railcar bogie in which a vibrationproof rubber between an axle box and a bogie frame includes a vertical load fluctuation sensor in parallel with the vibrationproof rubber and configured to deform in conjunction with elastic deformation of the vibrationproof rubber in a vertical direction, the vibrationproof rubber supporting a downward load from the bogie frame. The vertical load fluctuation sensor changes an electric output by the deformation of the vertical load fluctuation sensor in conjunction with the elastic deformation of the vibrationproof rubber in the vertical direction.