A method of operating a wind turbine power generating apparatus includes a step of obtaining a wind direction of a wind; a step of obtaining at least one of a wind velocity of the wind or an index of turbulence degree of the wind velocity; and a step of selecting an operation mode of the wind turbine power generating apparatus from among a plurality of operation modes including a normal operation mode and at least one load-suppressing operation mode in which a load applied to a wind turbine blade is smaller than in the normal operation mode, on the basis of whether the at least one of the wind velocity or the index of turbulence degree is at least a threshold. The threshold of the at least one of the wind velocity or the index of turbulence degree is variable in accordance with the wind direction.