Embroidery unit attaching and detaching device and sewing machine

Provided with an embroidery unit attaching and detaching device capable of preventing an embroidery unit from falling from a sewing machine and capable of preventing the damage of a portion connecting the embroidery unit and the sewing machine even when the moment load of twisting the embroidery unit with respect to the sewing machine is applied. An embroidery unit attaching and detaching device includes: a lock mechanism configured to operate in association with a motion of an embroidery unit in an attaching direction to restrict the motion of the embroidery unit in a detaching direction with respect to a sewing machine; and support mechanisms for restricting a relative motion of the sewing machine and the embroidery unit in a vertical direction where recessed portions and protruded portions are engaged with each other.