This study investigated the occurrence and morphological characteristics of Polyphylla laticollis manchurica adults in the Miho River, Cheongju, from June to August 2024. Surveys were conducted at five sites along a 14 km stretch from upstream of Palgyeol Bridge to downstream of Oksan Bridge, including three sites along the main river and two sites in tributaries. No P. laticollis manchurica adults were found at the tributary sites. A total of 107 adults were recorded at site C and D, with peak occurrence observed between June 20 and August 4, 2024. The first occurrence date was recorded in June 20, the peak occurrence on July 5, and the last observation on August 4. The morphological measurements of the adults attracted by light trap were as follows: body length 33.38±1.68 mm; body width 16.02±1.00 mm; and body weight 1.45±0.32 g. The sex ratio (male : female) was 7.14 : 2.86. While no significant differences were observed in body length and width between males and females, females were significantly heavier during the third survey period. Most adults attracted to artificial light were males, and several dead individuals were found near streetlights and bridge. This study provides fundamental data on the occurrence period, habitat distribution, and phototactic behavior of P. l. manchurica, contributing to a better ecological understanding and conservation efforts for this endangered species.