A zoom lens with a reduced thickness and size in the depthwise direction consists of a plurality of lens groups (GR1 to GR5), so that it varies in power in response to variation in intervals between the lens groups. The zoom lens also has a prism G2 to bend the optical axis passing through the lens groups (GR1 to GR5). The last lens group G5 (counted from the object side) is composed of a negative lens group and a positive lens group, with an air layer interposed between them (arranged sequentially from the object side). The present invention also provides an imaging device equipped with an imaging element to convert the optical images formed by said zoom lens into electrical signals.