To provide a tension distribution measuring apparatus capable of accurately measuring tension distribution even in the case of a belt-like body with low density and a belt-like body with thin board thickness.

A tension measuring apparatus is constituted so as to accurately measure tension distribution in consideration of additional mass of the air in the surroundings to affect vibration of a belt-like body even in the case of a belt-like body with low density and a belt-like body with thin board thickness by being provided with: vibration load loading means 3 for loading a vibration load to a belt-like body 1 supported by support rolls 2a, 2b at two parts in the longitudinal direction; and displacement gauges 4 which measure vibration displacement to be generated by the vibration load loading means 3 at a plurality of measurement points 1a in the width direction of the belt-like body 1, calculating and measuring the tension distribution of the belt-like body 1 from characteristic frequencies and vibration modes of the belt-like body 1 to be calculated from the vibration displacement measured by the respective displacement gauges 4, mass of the belt-like body 1 between support parts, and additional mass of fluid contacting the belt-like body between the support parts.