To obtain a new strain of fine alga belonging to the genus Botryococcus braunii A race capable of producing a 33C hydrocarbon and to provide a method for efficiently culturing the strain.

This strain of Botryococcus braunii A race is a new fine alga belonging to the genus Botryococcus. A hydrocarbon produced by the alga of this strain contains a 33C hydrocarbon. The new strain of the fine alga belonging to the genus Botryococcus braunii A race is cultured under intermittently irradiating the strain with an artificial light preferably once daily for 5-15 hours.