The disclosed technology is directed to a treatment tool having a blade configured to engage with a treatment target. A heater is configured to be spaced apart from the blade. A first thermally conductive member is sandwiched between the blade and the heater so as to transmit heat to the blade. The first thermally conductive member includes respective first and second portions each of which is disposed on respective distal-end and proximal-end sides in longitudinal directions of the blade for thermally conducting a different prescribed quantity of heat per unit time from each of the respective first and second portions to the blade via the heater. The first thermally conductive member includes a first thermal conductivity anisotropy that is higher in longitudinal directions of the blade and is lower in widthwise directions transverse to the longitudinal directions.
