PROBLEM TO BE SOLVED: To provide a coating liquid for forming a gas barrier layer that allows production of a gas barrier layer capable of maintaining gas barrier properties by a cellulosic material even at high humidity, capable of preventing water vapor or the like serving as a deterioration factor from immersing or infiltrating inside a film, and with smaller humidity deterioration of film strength, and also to provide a manufacturing method thereof, a gas barrier laminate and a packaging material.SOLUTION: A coating liquid for forming a gas barrier layer includes a cellulose nanofiber, a water-soluble polymer, an inorganic laminar compound, and a water repellent. The fiber width of the cellulose nanofiber is, for instance, 3-50 nm. The coating liquid is applied, for instance, on one side of a base material 1 and then desiccated so as to form a gas barrier layer 2. The gas barrier layer 2 is capable of maintaining gas barrier properties by a cellulosic material even at high humidity, is capable of preventi
