Solid immersion lens unit and semiconductor inspection device

This solid immersion lens unit is provided with: a solid immersion lens; and a holder which holds the solid immersion lens such that the solid immersion lens is swingable. The solid immersion lens has: a first lens part which is made of a first material; and a second lens part which is made of a second material having a lower refractive index than the first material and which is joined to the first lens part. The first lens part includes: a contact surface which is to be brought into contact with an observation target object; and a first spherical surface which is convex. The second lens part includes: a second spherical surface which is concave and faces the first spherical surface; and a third spherical surface which is convex and is disposed so as to face an objective lens. The holder has a contact part which is configured to be capable of contact with the third spherical surface.