OPERATION DEVICE AND WORK MACHINE

[Problem] A technique capable of improving the operability of an expansion-type operation device is provided.[Solution] An exemplary operation device includes: a lever stand that is disposed on a side of a seat and has an operation lever; a lever stand support portion that supports the lever stand so that the lever stand is pivotable up and down; a base portion that is disposed below the lever stand support portion and supports the lever stand support portion so that the lever stand support portion is pivotable left and right; and a holding plate that is supported by the base portion and disposed above a bottom portion of the lever stand support portion. When the lever stand is pivoted from the first posture to the second posture, the lever stand support portion is made pivotable in a left-right direction to select a third posture or a fourth posture. The holding plate holds, in the third posture or the fourth posture, the lever stand support portion supporting the lever stand in the first posture.