Bark and ambrosia beetles are groups of insects that bore into host trees and live inside. Damages by these insects have been increasing and become serious problems. This study aimed to clarify factors influencing attacks of these insects on the Betulaceae trees in Hokkaido. The study was conducted at monarch birch stands (Betula maximowicziana, BM), and alder (Alnus hirsuta, AH) and white birch (Betula platyphylla, BP) plantations. Ethanol-baited traps were set at these sites. Sticky traps were set on BM trunks. Effects of seasonality, wood freshness, and bark moisture were determined by AH bait logs. Six species of ambrosia beetles and two bark beetle species were captured by ethanol-baited traps. Seasonal occurrence of the beetles by the ethanol-baited traps had one peak in 2015, but two in 2016. No target species were collected by the sticky traps. Wood freshness had stronger influence on the number of attacks on the AH bait logs than bark moisture. Regarding two major species, Xylosandrus germanus was strongly influenced by wood freshness but Platypus severini was not but by seasonal occurrence. The number of attacks had a strong positive correlation with log size in P. severini but weaker in X. germanus.