A method of producing methyl methacrylate comprising the following steps: Thermal decomposition step: a hydrocarbon having 3 or more carbon atoms is thermally decomposed to obtain a decomposed gas having a total content of propyne and propadiene of 2 wt % or more, Separation step: mixed liquid rich in propyne and propadiene is separated from the decomposed gas obtained in the thermal decomposition step, Propyne purification step: the mixed liquid rich in propyne and propadiene obtained in the separation step is subjected to extractive distillation, for separation into purified propyne, and crude propadiene containing propadiene as the main component, Isomerization step: the crude propadiene obtained in the propyne purification step is isomerized in the presence of an isomerization catalyst, to obtain crude propyne containing propyne as the main component, and Carbonylation step: the purified propyne obtained in the propyne purification step is reacted with carbon monoxide and methanol in the presence of a group VIII metal catalyst system, to produce methyl methacrylate.