An air inflation device includes an inflation unit having an air outlet channel extending along a first axis, and an insertion channel extending along a second axis transverse to the first axis and partially communicating with the air outlet channel. A pressure gauge unit is rotatably mounted on the inflation unit and includes a pressure gauge, and a shaft extending outwardly from the pressure gauge and inserted into the air outlet channel. The shaft has an annular groove formed in an outer peripheral surface thereof and corresponding to and communicating with the insertion channel. An air guide unit includes a manifold inserted into the insertion channel and engaging the annular groove.