Feed screw mechanism and electric actuator

A feed screw mechanism that converts rotary motions of an electric motor into linear motions and transmits the linear motions to an operation target, the feed screw mechanism comprising:

• a rotary member having a female screw portion on an inner peripheral surface;
• a linear motion member having, on an outer peripheral surface, a male screw portion that is directly or indirectly engaged with the female screw portion and making a linear motion with rotation of the rotary member;
• a lubricant housed between the female screw portion and the male screw portion;
• a housing that houses the rotary member and the linear motion member;
• and
• a wall portion protruding, in a radial direction, from the outer peripheral surface of the linear motion member, wherein
• the wall portion is configured to move linearly together with the linear motion member,
• the wall portion is disposed so as not to contact an inner peripheral surface of the housing and a member provided on the inner peripheral surface of the housing, and
• only a part of an outer perimeter of the wall portion is larger than an inner diameter of the female screw portion of the rotary member.