This thesis follows a topic of visible and invisible in the poetry and the essays of the Spanish writer active in the second half of the 20th century, José Ángel Valente. It situates the author in his historical and literary context and presents the evolution of his work. After that, it focuses on three of Valente's sources of inspiration and it outlines the conception of speech and artwork in Heidegger, the approach to space of sculptor Eduardo Chillida and the work with matter of painter Antoni Tàpies. The visible and the invisible are indirectly observed in Valente by means of more or less concrete representation and relationship to the reality, in visual characteristics, such as light and darkness, colours and shapes, and in the problematics of the sight. The visibility, the invisibility and the transparency directly manifest themselves in Valente's conception of matter and form and the word's manifestation and they also appear as motifs in his texts.