Abstract: Disclosed is an anti-vibration device of an input/output shaft for a manual transmission of a vehicle, capable of absorbing vibration of input/output shafts so that the input/output shafts are prevented from being bent. The anti-vibration device of the input/output shafts for a manual transmission having a first shaft receiving power of an engine and a second shaft transmitting power through a stage driving gear formed on the first shaft. The anti-vibration device includes a transmission housing having an installation space provided therein with the first and second shafts, and at least one anti-vibration unit provided in the transmission housing perpendicularly to an axial direction of the first and second shafts. The anti-vibration unit is a support wall integrated with the transmission housing to absorb vibration so that the first and second shafts are prevented from being bent in directions opposite to each other.