Olefin production method

A method for producing an olefin from plastic containing a polyolefin, the method comprising:

• a cracking step of thermally cracking the plastic to obtain a cracked gas,
• wherein a temperature T4 of the cracked gas at a gas outlet of a cracking device in which the cracking step is carried out is not lower than a dew point of the cracked gas.

A method for producing an olefin from plastic containing a polyolefin, the method comprising:

• a cracking step of thermally cracking the plastic to obtain a cracked gas,
• wherein T5-T6≤200 (° C.) where T5 (° C.) is a cracking temperature set in the cracking step, and T6 (° C.) is a temperature of the cracked gas at a gas outlet of a cracking device in which the cracking step is carried out.