A rubber foam tube (5) is produced by extruding a rubber composition into a tubular body (4) and feeding the tubular body (4) in an elongated state without cutting to pass the tubular body (4) through a microwave crosslinking device (8) and then through a hot air crosslinking device (9) for continuously foaming and crosslinking the rubber composition. At this time, a ratio V2/V1 between a speed V2 at which the tubular body (4) passes through the hot air crosslinking device (9) and a speed V1 at which the tubular body (4) passes through the microwave crosslinking device (8) is not less than 1.0 and not greater than 1.6.