A torque estimation system comprising: a yaw actuator configured to be included in a wind turbine; a plurality of bolts configured to fix the yaw actuator to a fixation portion; a load portion configured to apply to a drive shaft of a drive unit of the yaw actuator a torque simulating a load caused by wind force, before operation of the wind turbine; a plurality of torque meters configured to be installed on the bolts, and to measure the torque applied to the drive shaft by the load portion; and a torque estimation device, wherein the torque estimation device includes: a strain amount obtaining unit configured to obtain an amount of strain in the bolts, before and during operation of the wind turbine; a generation unit configured to generate pre-operation information representing correspondence between the torque applied to the drive shaft by the load portion and measured by the torque meters, and the measurement results of the amount of strain of the bolts caused by the torque of the load portion and obtained by the strain amount obtaining unit, before operation of the wind turbine; a storage unit configured to store pre-operation information and characteristic information of the drive unit; and an estimation unit configured to estimate a torque occurring in the drive shaft during operation of the wind turbine, characterized in that the generation unit further generates correspondence information based on a torque occurring in the drive shaft during operation of the wind turbine, the amount of strain obtained by the strain amount obtaining unit during operation of the wind turbine, the pre-operation information, and the characteristic information, the storage unit further stores the correspondence information, and the estimation unit estimates the torque occurring in the drive shaft based on the amount of strain obtained by the strain amount obtaining unit and the correspondence information, during operation of the wind turbine. a yaw actuator configured to be included in a wind turbine; a plurality of bolts configured to fix the yaw actuator to a fixation portion; a load portion configured to apply to a drive shaft of a drive unit of the yaw actuator a torque simulating a load caused by wind force, before operation of the wind turbine; a plurality of torque meters configured to be installed on the bolts, and to measure the torque applied to the drive shaft by the load portion; and a torque estimation device, wherein the torque estimation device includes: a strain amount obtaining unit configured to obtain an amount of strain in the bolts, before and during operation of the wind turbine; a generation unit configured to generate pre-operation information representing correspondence between the torque applied to the drive shaft by the load portion and measured by the torque meters, and the measurement results of the amount of strain of the bolts caused by the torque of the load portion and obtained by the strain amount obtaining unit, before operation of the wind turbine; a storage unit configured to store pre-operation information and characteristic information of the drive unit; and an estimation unit configured to estimate a torque occurring in the drive shaft during operation of the wind turbine, characterized in that the generation unit further generates correspondence information based on a torque occurring in the drive shaft during operation of the wind turbine, the amount of strain obtained by the strain amount obtaining unit during operation of the wind turbine, the pre-operation information, and the characteristic information, the storage unit further stores the correspondence information, and the estimation unit estimates the torque occurring in the drive shaft based on the amount of strain obtained by the strain amount obtaining unit and the correspondence information, during operation of the wind turbine. a strain amount obtaining unit configured to obtain an amount of strain in the bolts, before and during operation of the wind turbine; a generation unit configured to generate pre-operation information representing correspondence between the torque applied to the drive shaft by the load portion and measured by the torque meters, and the measurement results of the amount of strain of the bolts caused by the torque of the load portion and obtained by the strain amount obtaining unit, before operation of the wind turbine; a storage unit configured to store pre-operation information and characteristic information of the drive unit; and an estimation unit configured to estimate a torque occurring in the drive shaft during operation of the wind turbine, characterized in that the generation unit further generates correspondence information based on a torque occurring in the drive shaft during operation of the wind turbine, the amount of strain obtained by the strain amount obtaining unit during operation of the wind turbine, the pre-operation information, and the characteristic information, the storage unit further stores the correspondence information, and the estimation unit estimates the torque occurring in the drive shaft based on the amount of strain obtained by the strain amount obtaining unit and the correspondence information, during operation of the wind turbine.