A fuel property determination method of determining an octane number of a fuel using a device, the method comprising the device enacting: a reaction mechanism analysis process (S 1) comprising: calculating simulation data using elementary reaction data including a plurality of elementary reaction formulae that describe chemical reactions and parameters that are associated with the elementary reaction formulae, and computation data including equations that are time-one-dimensionalized in zero-dimensional space, in which the independent variable is time and the dependent variables are concentration and temperature and positions are not included in the parameters, for calculating the simulation data from the elementary reaction data; characterised by determining whether or not experiment data including a one-dimensional space temperature distribution at a time of the chemical reactions can be derived from the simulation data; and if the experiment data cannot be derived from the simulation data: adjusting (S 13) parameters that are included in the elementary reaction data and recalculating the simulation data using the adjusted parameters; and if the experiment data cannot be derived from the simulation data using the adjusted parameters, repeatedly adjusting the parameters and calculating simulation data using the adjusted parameters until the experiment data can be derived from the simulation data; and an octane number determination process of calculating combustion characteristics of the fuel by performing a simulation based on the simulation data and determining the octane number of the fuel based on the combustion characteristics of the fuel. a reaction mechanism analysis process (S 1) comprising: calculating simulation data using elementary reaction data including a plurality of elementary reaction formulae that describe chemical reactions and parameters that are associated with the elementary reaction formulae, and computation data including equations that are time-one-dimensionalized in zero-dimensional space, in which the independent variable is time and the dependent variables are concentration and temperature and positions are not included in the parameters, for calculating the simulation data from the elementary reaction data; characterised by determining whether or not experiment data including a one-dimensional space temperature distribution at a time of the chemical reactions can be derived from the simulation data; and if the experiment data cannot be derived from the simulation data: adjusting (S 13) parameters that are included in the elementary reaction data and recalculating the simulation data using the adjusted parameters; and if the experiment data cannot be derived from the simulation data using the adjusted parameters, repeatedly adjusting the parameters and calculating simulation data using the adjusted parameters until the experiment data can be derived from the simulation data; and an octane number determination process of calculating combustion characteristics of the fuel by performing a simulation based on the simulation data and determining the octane number of the fuel based on the combustion characteristics of the fuel. calculating simulation data using elementary reaction data including a plurality of elementary reaction formulae that describe chemical reactions and parameters that are associated with the elementary reaction formulae, and computation data including equations that are time-one-dimensionalized in zero-dimensional space, in which the independent variable is time and the dependent variables are concentration and temperature and positions are not included in the parameters, for calculating the simulation data from the elementary reaction data; characterised by determining whether or not experiment data including a one-dimensional space temperature distribution at a time of the chemical reactions can be derived from the simulation data; and if the experiment data cannot be derived from the simulation data: adjusting (S 13) parameters that are included in the elementary reaction data and recalculating the simulation data using the adjusted parameters; and if the experiment data cannot be derived from the simulation data using the adjusted parameters, repeatedly adjusting the parameters and calculating simulation data using the adjusted parameters until the experiment data can be derived from the simulation data; and an octane number determination process of calculating combustion characteristics of the fuel by performing a simulation based on the simulation data and determining the octane number of the fuel based on the combustion characteristics of the fuel. adjusting (S 13) parameters that are included in the elementary reaction data and recalculating the simulation data using the adjusted parameters; and if the experiment data cannot be derived from the simulation data using the adjusted parameters, repeatedly adjusting the parameters and calculating simulation data using the adjusted parameters until the experiment data can be derived from the simulation data; and an octane number determination process of calculating combustion characteristics of the fuel by performing a simulation based on the simulation data and determining the octane number of the fuel based on the combustion characteristics of the fuel.