A motor-driven compressor comprising: a compression mechanism configured to compress fluid; an electric motor configured to drive the compression mechanism ; an inverter configured to control driving of the electric motor ; a housing that accommodates the compression mechanism and the electric motor ; and a cover fastened to the housing by fasteners , the cover defining an accommodation chamber with the housing to accommodate the inverter , wherein the cover includes a plate-shaped body wall , and insertion holes extending through a periphery of the body wall , the fasteners being inserted through the insertion holes , and the body wall includes a first surface opposed to the inverter in the accommodation chamber , a second surface located at a side opposite from the first surface , a first thickness portion having a first thickness (Tl), and a second thickness portion located around at least one of the insertion holes , wherein the second thickness portion has a second thickness (T2) that is smaller than the first thickness (T1) and is obtained by recessing the body wall from the first surface toward the second surface , characterized in that the cover includes a circumferential wall extending from an outer edge of the body wall toward the housing , the insertion holes extend through the body wall and the circumferential wall , each of the second thickness portions extends around a corresponding one of the insertion holes to be concentric to the insertion hole , and opposite ends of the second thickness portion in a circumferential direction connect to the circumferential wall . a compression mechanism configured to compress fluid; an electric motor configured to drive the compression mechanism ; an inverter configured to control driving of the electric motor ; a housing that accommodates the compression mechanism and the electric motor ; and a cover fastened to the housing by fasteners , the cover defining an accommodation chamber with the housing to accommodate the inverter , wherein the cover includes a plate-shaped body wall , and insertion holes extending through a periphery of the body wall , the fasteners being inserted through the insertion holes , and a plate-shaped body wall , and insertion holes extending through a periphery of the body wall , the fasteners being inserted through the insertion holes , and the body wall includes a first surface opposed to the inverter in the accommodation chamber , a second surface located at a side opposite from the first surface , a first thickness portion having a first thickness (Tl), and a second thickness portion located around at least one of the insertion holes , wherein the second thickness portion has a second thickness (T2) that is smaller than the first thickness (T1) and is obtained by recessing the body wall from the first surface toward the second surface , a first surface opposed to the inverter in the accommodation chamber , a second surface located at a side opposite from the first surface , a first thickness portion having a first thickness (Tl), and a second thickness portion located around at least one of the insertion holes , wherein the second thickness portion has a second thickness (T2) that is smaller than the first thickness (T1) and is obtained by recessing the body wall from the first surface toward the second surface , characterized in that the cover includes a circumferential wall extending from an outer edge of the body wall toward the housing , the insertion holes extend through the body wall and the circumferential wall , each of the second thickness portions extends around a corresponding one of the insertion holes to be concentric to the insertion hole , and opposite ends of the second thickness portion in a circumferential direction connect to the circumferential wall . <EOS>