An air/gas mixing device, particularly for pre-mixing burner apparatuses, comprising: - first conveying means with centripetal flow including a plurality of ducts having a predominant radial direction and disposed along a circumferential profile concentric with a main axis and having a divergent configuration in the direction of the flow conveyed, the flow of air, intended for mixing with the gas, being intended to be admitted into said ducts, - second gas conveying means for conveying the gas, admitted into the device, into each duct of the first conveying means, such that in each duct air/gas pre-mixing takes place downstream of the zone for admission of the gas into the duct, in the direction of said axis, said second conveying means comprising a gas-distributing channel extending along a circular profile concentric with said main axis and also provided with a plurality of respective through openings, each of which places the channel in communication with a respective duct of the first conveying means, each duct of said plurality being delimited at least by a pair of opposed walls facing each other and rising in the same direction from a discoid base of said device, arranged for coaxial mounting with a fan, the duct being capable of being delimited, on the opposite side from the base, by at least part of a manifold for housing the impeller of the fan, each duct being open at the opposed ends of its length, with a first opening for the entry of the flow at one of the ends, in a position remote from the main axis of the base, and with a second opening for the exit of the flow at the other end, positioned in proximity to said axis, wherein the corresponding opening for communication of the channel with the corresponding duct is disposed in a position between said ends, and wherein the passage cross-section for the flow in each conveying duct has an amplitude increasing from the entry opening in the direction of the exit opening for the flow, such that the air/gas mixing, between the flow of air, conveyed along each duct, and the flow of combustible gas, fed via said channel into the corresponding opening, takes place in a section of the duct from which a divergent portion of the duct itself extends in the direction of the main axis. - first conveying means with centripetal flow including a plurality of ducts having a predominant radial direction and disposed along a circumferential profile concentric with a main axis and having a divergent configuration in the direction of the flow conveyed, the flow of air, intended for mixing with the gas, being intended to be admitted into said ducts, - second gas conveying means for conveying the gas, admitted into the device, into each duct of the first conveying means, such that in each duct air/gas pre-mixing takes place downstream of the zone for admission of the gas into the duct, in the direction of said axis, said second conveying means comprising a gas-distributing channel extending along a circular profile concentric with said main axis and also provided with a plurality of respective through openings, each of which places the channel in communication with a respective duct of the first conveying means, each duct of said plurality being delimited at least by a pair of opposed walls facing each other and rising in the same direction from a discoid base of said device, arranged for coaxial mounting with a fan, the duct being capable of being delimited, on the opposite side from the base, by at least part of a manifold for housing the impeller of the fan, each duct being open at the opposed ends of its length, with a first opening for the entry of the flow at one of the ends, in a position remote from the main axis of the base, and with a second opening for the exit of the flow at the other end, positioned in proximity to said axis, wherein the corresponding opening for communication of the channel with the corresponding duct is disposed in a position between said ends, and wherein the passage cross-section for the flow in each conveying duct has an amplitude increasing from the entry opening in the direction of the exit opening for the flow, such that the air/gas mixing, between the flow of air, conveyed along each duct, and the flow of combustible gas, fed via said channel into the corresponding opening, takes place in a section of the duct from which a divergent portion of the duct itself extends in the direction of the main axis.