Layered metal chalcogenide materials have been paid attention for potential thermoelectric materials due to their intrinsic low thermal conductivity due to their weak atomic boning between layers. Indium selenide InSe crystal is known to have low thermal conductivity in range of ~0.37 – 1.2 Wm-1K-1, while their intrinsic carrier concentration is quite low as ~1014 cm-3 due to the relatively large bandgap of 1.2 eV. Therefore, InSe-based materials can be good candidates for thermoelectric materials, if the carrier concentration can be increased by proper doping. Here, we investigated the electronic and thermal properties of the series of Si-doped InSe, In1-xSixSe polycrystalline samples. The cation substitution of Si increased electrical conductivity, while decreasing activation energy for the electrical conductivity. The negative Seebeck coefficient increased as Si doping increases, resulting in large enhancement in power factor. The slight reduction of thermal conductivity was also observed by the doping. As results, the thermoelectric figure of merit zT value was expected to higher than 0.2 at high temperature, which can offer possibility for InSe-based thermoelectric materials. The improvement of thermoelectric properties is related with simultaneous increase of σ and S with Si doping, which will be discussed based on the interrelationship between two kinds of electrons contributing to charge transport in InSe; (1) high mobility electrons in the conduction band and (2) low-moblity electrons in the 2D electric subbands.