A vehicle interior illumination device, comprising: an illumination lamp that can be provided in a vehicle interior and is configured to be turned on to illuminate the vehicle interior, the illumination lamp includes a personal lamp configured to illuminate a seat and being turned on/off by a personal switch which can be operated by a passenger sitting on the seat; a detector (52, 53, 54, 55) that detects a condition to have the personal lamp to be turned on; a controller that controls a lighting of the personal lamp, such that the personal lamp lights with a first light amount or a second light amount smaller than the first light amount; and an instruction portion that can be operated by a driver and that is configured to instruct a low illuminance mode for lighting the personal lamp with the second light amount characterised in that when the condition is detected by the detector (52, 53, 54, 55) or when the personal switch is turned on, the controller lights the personal lamp with the first light amount; when the condition is not detected by the detector (52, 53, 54, 55), the personal switch is turned off and the low illuminance mode is instructed by the instruction portion, the controller lights the personal lamp with the second light amount, when the condition is not detected by the detector (52, 53, 54, 55), the personal switch is turned off and the low illuminance mode is not instructed by the instruction portion, the controller turns off the personal lamp, and when the condition is detected by the detector (52, 53, 54, 55), while the personal lamp is lit with the second light amount, the controller cancels the low illuminance mode and lights the personal lamp with the first light amount, and thereafter, when the condition becomes undetected, the controller sets the low illuminance mode again and lights the personal lamp with the second light amount. an illumination lamp that can be provided in a vehicle interior and is configured to be turned on to illuminate the vehicle interior, the illumination lamp includes a personal lamp configured to illuminate a seat and being turned on/off by a personal switch which can be operated by a passenger sitting on the seat; a detector (52, 53, 54, 55) that detects a condition to have the personal lamp to be turned on; a controller that controls a lighting of the personal lamp, such that the personal lamp lights with a first light amount or a second light amount smaller than the first light amount; and an instruction portion that can be operated by a driver and that is configured to instruct a low illuminance mode for lighting the personal lamp with the second light amount characterised in that when the condition is detected by the detector (52, 53, 54, 55) or when the personal switch is turned on, the controller lights the personal lamp with the first light amount; when the condition is not detected by the detector (52, 53, 54, 55), the personal switch is turned off and the low illuminance mode is instructed by the instruction portion, the controller lights the personal lamp with the second light amount, when the condition is not detected by the detector (52, 53, 54, 55), the personal switch is turned off and the low illuminance mode is not instructed by the instruction portion, the controller turns off the personal lamp, and when the condition is detected by the detector (52, 53, 54, 55), while the personal lamp is lit with the second light amount, the controller cancels the low illuminance mode and lights the personal lamp with the first light amount, and thereafter, when the condition becomes undetected, the controller sets the low illuminance mode again and lights the personal lamp with the second light amount.