In the present work temperature dependence of heat capacity of vitamin B 2 (riboflavin) has been measured for the first time in the range from 6 to 322K by precision adiabatic vacuum calorimetry. Based on the experimental data, the thermodynamic functions of the vitamin B 2 , namely, the heat capacity, enthalpy H°(T)−H°(0), entropy S°(T)−S°(0) and Gibbs function G°(T)−H°(0) have been determined for the range from T→0 to 322K. The value of the fractal dimension D in the function of multifractal generalization of Debye's theory of the heat capacity of solids was estimated and the character of heterodynamics of structure was detected. In a calorimeter with a static bomb and an isothermal shield, the energy of combustion of the riboflavin has been measured at 298.15K. The enthalpy of combustion Δ c H° and the thermodynamic parameters Δ f H°, Δ f S°, Δ f G° and of reaction of formation of the riboflavin from simple substances at T=298.15K and p=0.1MPa have been calculated.