The invention provides an eyepiece optical system for head-mounted display and a head-mounted display device. The eyepiece optical system comprises a first lens, a second lens and a third lens, wherein the three lenses are arranged sequentially and coaxially from a human eye to an image source along the optical axis direction. The first lens and the second lens together form a cemented doublet and the combined focal power of the cemented doublet is a positive value. The surface of the second lens, closer to the side of the image source, is convex to the image source. The two optical surfaces of the third lens are the same in curvature direction and are concave to the image source. At the same time, the effective focal length of the cemented doublet, the effective focal length of the third lens and the effective focal length of the eyepiece optical system satisfy a certain relation. The interval between the cemented doublet and the third lens and the length of the system also satisfy a certain relation. The head-mounted display device comprises the above eyepiece optical system, an image display and a structure bracket. The display size of the image display and the pixel size of the image display satisfy a certain relation so as to realize a better experience effect. The eyepiece optical system and the head-mounted display device are large in field of view, low in distortion, low in color difference, and uniform in imaging effect.