Damper and method for manufacturing damper

A method for manufacturing a damper, comprising:

• a process of molding a housing member wherein a bottom portion is formed at one end of an outer cylinder portion formed in a cylinder shape, an open end portion is formed at another end of the outer cylinder portion, and a groove portion is formed on an inner periphery;
• and
• a process of molding a lid member wherein a movable member housed in the housing member is provided, and a projection portion engaging the groove portion is formed,
• wherein the housing member and the lid member are integrated to manufacture a damper,
• the method further comprising,
• a process of molding a thin wall portion which is thinner than the outer cylinder portion on a groove portion side more than an intermediate portion between the groove portion and the bottom portion in the outer cylinder portion.