Illumination device and illumination system

[Object] In an illumination device, to improve workability at the time of electrical connection to an external device, and reduce arrangement restriction occurring in association with the connection. [Means for Settlement] An illumination device 1 is provided with: a light source part 2; and an attachment part 3 that is attached on a non-light emitting surface side of the light source part 2. The attachment part 3 has: a circuit board that controls lighting of the light source part 2; and a connecting terminal 4 that is connected with a lead 13 for making an electrical connection between the circuit board and an external device. The connecting terminal 4 is arranged with being displaced inward rather than toward an outer peripheral end part of an attachment surface 3a for the light source part 2 in the attachment part 3. In a state where the light source part 2 is attached with the attachment part 3, between the light source part 2 and the attachment part 3, a gap is formed. Based on this, a space that contains the leads 13 is ensured, and therefore at the time of the electrical connection to the external device, even in the case where depending on arrangement, the lead 13 is bent to require an extra space, the space can be ensured to improve workability. Also, arrangement restriction for ensuring the space that contains the lead 13 can be eliminated.