A discharge tube is disclosed that includes: an airtight tube having first and second end surfaces each including a metallized surface; first and second discharge electrodes joined to the respective metallized surfaces; and multiple trigger lines formed on the inner wall surface of the airtight tube to extend along the axial directions of the airtight tube. The first and second discharge electrodes are joined to the metallized surfaces so that a discharge gap is formed between the first and second discharge electrodes and the airtight tube is hermetically sealed. The trigger lines include one or more first trigger lines connected to the metallized surfaces and multiple second trigger lines isolated from the metallized surfaces. The second trigger lines are formed at equal intervals on the inner wall surface of the airtight tube and each first trigger line is formed between a corresponding pair of the second trigger lines.
