This transmission device is provided with a transmission shaft (2), a cylindrical shaft member (3) and a planetary gear mechanism having a carrier. An in-shaft oil path (21) is formed in the transmission shaft (2). A radially inner portion (IP) of the carrier and the cylindrical shaft member (3) are linked by splines, an inside opening (55) of an induction oil path (51) is formed in a non-spline portion (NP) in the radially inner portion (IP), and a target race member (61) of a thrust bearing (60) is arranged abutting against the carrier. The radially innermost position of the non-spline portion (NP) is located radially outside of the radially outermost position of the spline engagement area (A), and the cylindrical shaft member (3), the non-spline portion (NP) and the target race member (61) form an oil receiving area (OR).