This paper proposes a method to provide an articulatory diagnosis of English produced by Korean learners using articulatory Goodness-Of-Pronunciation (aGOP) features, which are based on the distinctive feature theory in phonology. Previous studies on mispronunciation diagnosis have mainly dealt with pronunciation errors at phone-level. They inform learners of which phone is recognized as a diagnosis, when the corresponding segment is realized as a mispronunciation. However, to provide learners more effective corrective feedback, diagnosis had better be performed at articulatory-level, such as place and manner of articulation, rather than at phone-level. This study aims to provide automatic articulatory diagnosis using articulationbased confidence scores. At first, the speech of learners is forced-aligned and recognized to compute the GOP and aGOPs. When the forced-aligned segment is a consonant, articulatory diagnosis is conducted in three articulatory categories: voicing, place of articulation, and manner of articulation. Otherwise, diagnosis is performed in terms of rounding, height, and backness corresponding to articulatory characteristics of vowels. Experimental results show that F1 scores for voicing, place, and manner corresponding to consonants are 0.828, 0.754, and 0.781, respectively, whereas F1 score for rounding, height, and backness corresponding to vowels are 0.843, 0.782, and 0.824, respectively. These results indicate that the proposed method yields effective articulatory diagnosis.