The present invention relates to a high-resolution imaging optical system. The imaging optical system of the present invention comprises a first lens which has positive refractive power in order from an object side and in which an object side surface is convex toward the object side; a second lens which has negative refractive power and in which an upper side surface is concave toward the upper side; a third lens which has positive refractive power; a fourth lens which has negative refractive power; a fifth lens which has positive refractive power and in which the upper side surface is convex toward the upper side; and a sixth lens which has negative refractive power and in which the upper side surface is concave toward the upper side.
