Method for manufacturing filter unit

A method for manufacturing a filter unit for removing foreign matter in a liquid supplied to a liquid ejection head configured to eject the liquid, the method comprising:

• a first setting step of setting a filter portion in a setting portion provided in a first base portion;
• a welding step of welding the filter portion set on the setting portion and the first base portion by bringing a first heater unit into contact with a protruding portion provided in the first base portion to melt the protruding portion;
• and
• a separating step of separating the first heater unit from the filter portion, wherein
• the protruding portion before being melted protrudes from the filter portion set on the setting portion in a first direction orthogonal to a surface of the filter portion, and
• in the filter portion before being set on the setting portion and welded, a positioning portion provided at an end portion is in contact with the setting portion, and a part of the filter portion protrudes from the positioning portion in a second direction opposite to the first direction.